analysis of rank measures of association for ordinal data from longitudinal studies abstract consideration is given to longitudinal data settings in which an ordinal response variable is observed at two or more visits for each subject in two or more ordered groups with at least moderately large sample sizes e g overall n 40 rank measures of association between group and response are constructed at each time and the covariance matrix of these measures is also estimated variation among the rank measures of association is then analyzed through weighted least squares methods with weights based on the estimated covariance matrix such methods permit evaluation of group visit interaction as well as other effects of interest extensions of this type of analysis to situations with stratification or concomitant variables or missing data are also considered examples are provided for illustrative purposes

non parametric analysis of covariance for confirmatory randomized clinical trials to evaluate dose response relationships in confirmatory randomized clinical trials that are designed to compare multiple doses of a test treatment with a control group and with one another there are often statistical issues regarding compound hypotheses and multiple comparisons which need to be considered in most cases the analysis plan needs a clear specification for the proposed order for conducting statistical tests or for managing the overall significance level which statistical methods will be used and whether adjustment for covariates will be performed there are several benefits of specifying non parametric analysis of covariance ancova for performing the primary confirmatory analyses only minimal assumptions are needed beyond randomization in the study design whereas regression model based methods have assumptions about model fit for which departures may require modifications that are incompatible with a fully prespecified analysis plan non parametric methods provide traditionally expected results of ancova namely a typically small adjustment to the estimate for a treatment comparison so as to account for random imbalance of covariates between treatment groups and variance reduction for this estimate when covariates are strongly correlated with the response of interest the application of non parametric ancova is illustrated for two randomized clinical trials the first has a 3 x 4 factorial response surface design for the comparison of 12 treatments that is combinations of three doses of one drug and four doses of a second drug for change in blood pressure and the second example addresses the comparison of three doses of test treatment and placebo for time to disease progression this clinical trial has comparisons among treatments made for a dichotomous criterion wilcoxon rank scores and averages of cumulative survival rates in each example the non parametric covariance method provides variance reduction relative to its unadjusted counterpart

multivariate non parametric methods for mann whitney statistics to analyse cross over studies with two treatment sequences a non parametric strategy for the analysis of ordinal data from cross over studies with two treatment sequences and d or 2 periods is examined through mann whitney rank measures of association for each period these statistics estimate the probability of larger response for a randomly selected patient in one group relative to a randomly selected patient in the other group such estimates are as well formed for comparisons between groups for u pairs of periods with the same treatment methods for u statistics are used to produce a consistent estimate of the covariance matrix for the d u mann whitney estimates the effects of periods and treatments on the respective mann whitney estimates are evaluated through linear or log linear models for estimation of the parameters in these models a modified weighted least squares method is applied through a 2d 1 or d u dimensional basis which effectively addresses potentially near singularities in the estimated covariance matrix of the mann whitney estimates the proposed methods are applicable to response variables with an interval or an ordered categorical scale their scope additionally has capabilities for controlling strata in the design of a cross over study or concomitant variables for which covariance adjustment is of interest for reduction of variance applications of the methods are illustrated through three cross over studies with different specifications for the two sequences of two treatments during two to four periods

survey paper static output feedback a survey this paper reviews the static output feedback problem in the control of linear time invariant lti systems it includes analytical and computational methods and presents in a unified fashion the knowledge gained in the decades of research into this important open problem the paper shows that although many approaches and techniques exist to approach different versions of the problem no efficient algorithmic solutions are available

characterizing the manifest probabilities of latent trait models the problem of characterizing the manifest probabilities of a latent trait model is considered the item characteristic curve is transformed to the item passing odds curve and a corresponding transformation is made on the distribution of ability this results in a useful expression for the manifest probabilities of any latent trait model the result is then applied to give a characterization of the rasch model as a log linear model for a 2 j contingency table partial results are also obtained for other models the question of the identifiability of guessing parameters is also discussed

simulation of the effects of loudness recruitment and threshold elevation on the intelligibility of speech in quiet and in a background of speech these experiments simulated the threshold elevation and loudness recruitment associated with three different types of cochlear hearing loss moderate flat condition r2 severe flat condition r3 and moderate to severe sloping condition rx this was done to allow an examination of the effects of these factors on the intelligibility of speech in isolation from other factors that are normally associated with cochlear hearing loss such as reduced frequency selectivity the simulation was performed by splitting the input signal into 13 frequency bands and processing the envelope in each band so as to create loudness sensations in a normal ear that would resemble those produced in an impaired ear with recruitment the bands were then recombined all tests were performed using subjects with normal hearing for speech in quiet simulation of hearing loss produced a reduction in the ability to understand low level speech however speech at sufficiently high levels was highly intelligible in all conditions linear amplification according to the national acoustic laboratory nal prescription gave high intelligibility for speech at normal conversational levels for speech presented at a fixed input level of 65 db spl against a background of a single competing talker simulation of hearing loss produced substantial decrements in performance the speech to background ratios in conditions r2 and rx had to be 11 13 db higher than in the control condition unprocessed stimuli to achieve similar levels of performance linear amplification according to the nal prescription improved performance markedly for the conditions simulating flat losses but was less effective for the condition simulating a sloping loss this indicates that threshold elevation combined with recruitment produces a loss of intelligibility for speech in the presence of a single competing talker that is only partly compensated by linear amplification of the type typically used in hearing aids

effects of level and frequency on the detection of decrements and increments in sinusoids thresholds for the detection of decrements in level of sinusoidal signals were measured as a function of decrement duration level 25 40 55 and 70 db spl and frequency 250 1000 and 4000 hz in eleven normally hearing subjects thresholds for detecting a brief increment in level were also measured the sinusoids were presented in a background noise intended to mask spectral splatter associated with the decrement or increment performance tended to worsen with decreasing frequency for all decrement durations and for increment detection performance also worsened with decreasing level the results were analyzed using a model consisting of a compressive nonlinearity a sliding temporal integrator and a decision device the analysis indicated that the worsening in performance with decreasing frequency and decreasing level can be attributed partly to increases in the equivalent rectangular duration erd of the temporal integrator but mainly to changes in the efficiency of the detection process following the temporal integrator at lower frequencies and levels a larger change is required at the output of the integrator for threshold to be reached at each frequency the erd was relatively invariant with level for levels more than about 20 db above the absolute threshold

phoneme recognition as a function of the number of auditory filter outputs it has been proposed that listeners take advantage of brief coups d oeil when processing speech in noise these glimpses can be characterized both in time and frequency the obligatory role of the auditory filters in determining the nature of any further processing suggests that the frequency extent of a glimpse should be equivalent to that of an auditory filter accordingly it is hypothesized that the spectral characteristics of glimpses primarily relate to the available number of auditory channels the present study investigated the number of auditory filter outputs needed to identify phonemes in quiet stimuli were first restricted to 80 8000 hz and then split into 30 contiguous auditory filter width bands normal hearing listeners were presented with n bands whose spectral location was selected randomly from trial to trial no signal was presented in the other bands consistent with previous studies performance gradually increased with the number of bands an asymptote was reached with 24 and 16 bands for vowels and consonants respectively while high levels of speech understanding are typically observed with as few as 4 channels of spectral information our results indicate that accurate phoneme recognition requires combination of a much larger number of auditory filter outputs

the analysis of repeated categorical measurements subject to nonignorable nonresponse abstract conditional likelihood methods have been proposed for analyzing the repeated measurement of categorical responses this article extends the methods to include partially classified subjects the extension allows for an ignorable or nonignorable nonresponse mechanism and uses standard statistical software for the computations two examples of incomplete longitudinal categorical data illustrate the method

masking of speech by amplitude modulated noise abstract the degree of masking of human speech by environmental noise may be influenced by amplitude variations in the noise the listener s condition with respect to age and auditory function may affect his sensitivity to such noise also fatigue effects are possible after prolonged exposure to masking noise these aspects have been tested in the present study the results show that in general amplitude modulation of a masking noise reduces its speech masking effect as compared to unmodulated noise of the same r m s sound level and spectrum age did not affect the release of masking found in am noise however hearing impaired listeners obtained much less release of speech masking than those with normal hearing small but statistically significant fatigue effects were found after up to 60 min exposure to noise at 60 db spl the speech to noise ratio needed for 30 correct speech recognition was significantly affected by both age and hearing loss

static output feedback controllers stability and convexity the main objective of this paper is to solve the following stabilizing output feedback control problem given matrices a b sub 2 c sub 2 with appropriate dimensions find if one exists a static output feedback gain l such that the closed loop matrix a b sub 2 lc sub 2 is asymptotically stable it is known that the existence of l is equivalent to the existence of a positive definite matrix belonging to a convex set such that its inverse belongs to another convex set conditions are provided for the convergence of an algorithm which decomposes the determination of the aforementioned matrix in a sequence of convex programs hence this paper provides a new sufficient but not necessary condition for the solvability of the above stabilizing output feedback control problem as a natural extension we also discuss a simple procedure for the determination of a stabilizing output feedback gain assuring good suboptimal performance with respect to a given quadratic index some examples borrowed from the literature are solved to illustrate the theoretical results

exact logistic regression theory and examples we provide an alternative to the maximum likelihood method for making inferences about the parameters of the logistic regression model the method is based appropriate permutational distributions of sufficient statistics it is useful for analysing small or unbalanced binary data with covariates it also applies to small sample clustered binary data we illustrate the method by analysing several biomedical data sets

analysis of repeated categorical data using generalized estimating equations moment methods for analysing repeated binary responses have been proposed by liang and zeger and extended by prentice and zhao and prentice in these estimating equations models are proposed for the correlation between the repeated binary responses we extend liang and zeger s method to models for the correlation between repeated nominal or ordinal categorical responses in particular when the repeated responses are binary our methods reduce to liang and zeger s method our method is illustrated with two datasets one dataset contains repeated observations of self assessment of arthritis an ordered variable with three categories collected during a randomized comparative study of alternative treatments of patients with rheumatoid arthritis the second dataset is a longitudinal study of the health effects of air pollution in which the repeated ordered multinomial response is the wheezing status no wheeze wheeze with cold wheeze apart from cold of a child at ages 9 10 11 and 12 years

latent variable models for the analysis of medical data with repeated measures of binary variables consideration of within subject dependencies is a key issue in modelling binary repeated measures medical data borrowing from recent developments in sociology and psychology we demonstrate the applicability of a latent variable approach to the analysis of such data in particular we present the rasch model as a basic model for representing the relationship of subject and treatment parameters the latent variable approach is useful in providing a theoretical framework for specifying dependencies exactly and also as a base for considering more complicated relationships between repeated measures variables

robust static output feedback controller synthesis using kharitonov s theorem and evolutionary algorithms this paper presents a simple but effective tuning strategy for robust static output feedback sof controllers with minimal quadratic cost in the context of multiple parametric uncertainties finding this type of controller is known to be computationally intractable using conventional techniques this is mainly due to the non convexity of the resulting control problem which has a fixed structure to solve this kind of control problem easily and directly without using any complicated mathematical manipulations we utilize kharitonov s theorem and an evolutionary algorithm ea for the resolution of the underlying constrained optimization problem using kharitonov s theorem a family of bounded robustly stable static output feedback controllers can be defined and ea is used to select the controller that ensures a minimal quadratic cost within this family the resulting tuning strategy is applicable to both stable and unstable systems without any limitations on the order of the process to be controlled a numerical study was conducted to demonstrate the validity of the proposed tuning procedure

a review of some statistical methods for covariance analysis of categorical data three general methods for covariance analysis of categorical data are reviewed and applied to an example from a clinical trial in rheumatoid arthritis the three methods considered are randomization model nonparametric procedures maximum likelihood logistic regression and weighted least squares analysis of correlated marginal functions a fourth heuristic approach the unweighted linear model analysis is an approximate procedure but it is easy to implement the assumptions and statistical issues for each method are discussed so as to emphasize philosophical differences between their rationales attention is given to computational differences but it is shown that the methods lead to similar results for analogous problems it is argued that the essential differences between the methods lie in their underlying assumptions and the generality of the conclusions which may be drawn

psychoacoustic and phonetic temporal processing in normal and hearing impaired listeners four measures of auditory temporal processing were obtained from 16 normals and 16 individuals with a hearing loss of heterogeneous origin these measures were 1 temporal integration the difference in detection thresholds between signals of 10 and 1000 ms duration which was determined to provide an estimate of the ability to integrate energy over time 2 gap detection the shortest duration of silence between two noise bursts that can be discriminated from an uninterrupted noise 3 temporal difference limen the increment in duration necessary to detect a difference in the duration of a noise burst 4 gap difference limen the increment in duration necessary to detect a difference in the duration of a silent interval between two noise bursts each measure was obtained for stimuli centered both at 500 and at 4000 hz using a three alternative forced choice procedure in addition measures of identification and discrimination were obtained for two sets of synthetic speech syllables varying chiefly in a temporal parameter voice onset time from ba to pa and from bi to pi finally speech identification in noise was measured with the faaf test most of the hearing impaired listeners displayed poorer temporal analysis than the normals on all of the psychoacoustical tasks regardless of whether the two groups were compared at similar sound pressure levels or at similar sensation levels although the hearing impaired listeners displayed a reduction in the ability to discriminate subphonemic cues for the voiced voiceless distinction their identification of that distinction in stop consonants appeared to be normal the hearing impaired group made about twice as many errors as did the normals on each of the consonant features of place manner and voicing when identifying speech in noise increased temporal difference limen and longer gap detection thresholds were found to correlate significantly with reduced speech intelligibility in noise even when the effects of the pure tone threshold loss were partialed out

speech reception by listeners with real and simulated hearing impairment effects of continuous and interrupted noise the effects of audibility and age on masking for sentences in continuous and interrupted noise were examined in listeners with real and simulated hearing loss the absolute thresholds of each of ten listeners with sensorineural hearing loss were simulated in normal hearing listeners through a combination of spectrally shaped threshold noise and multi band expansion for octave bands with center frequencies from 0 25 8 khz each individual hearing loss was simulated in two groups of three normal hearing listeners an age matched and a non age matched group the speech to noise ratio s n for 50 correct identification of hearing in noise test hint sentences was measured in backgrounds of continuous and temporally modulated 10 hz square wave noise at two overall levels for unprocessed speech and for speech that was amplified with the nal rp prescription the s n in both continuous and interrupted noise of the hearing impaired listeners was relatively well simulated in both groups of normal hearing listeners thus release from masking the difference in s n obtained in continuous versus interrupted noise appears to be determined primarily by audibility minimal age effects were observed in this small sample observed values of masking release were compared to predictions derived from intelligibility curves generated using the extended speech intelligibility index esii rhebergen et al 2006 j acoust soc am 120 3988 3997

growth of masking as a measure of response growth in hearing impaired listeners growth of masking functions were obtained from 19 normal and 5 hearing impaired listeners using a simultaneous masking paradigm when masker and probe frequency are identical the slope of masking approximates 1 0 for both normal hearing and impaired listeners for masker frequencies less than or greater than probe frequency the slopes for impaired listeners are shallower than those of normals these findings are consistent with previously reported physiological data single fiber rate versus level and ap masking functions for animals with induced cochlear lesions results are discussed in terms of a potential masking technique to estimate the growth of response in normal and impaired ears

distribution free fitting of logit models with random effects for repeated categorical responses this article discusses random effects models for within subject comparisons of repeated responses on the same categorical scale the models account for the correlation that normally occurs between repeated responses the standard way of fitting such models maximizes the marginal likelihood after integrating with respect to a distribution for the random effect an alternative non parametric approach does not assume a distributional form for the random effects recent literature shows that for certain simple logit models this approach yields essentially the same model parameter estimates as conditional maximum likelihood moreover these estimates also result from fitting corresponding quasi symmetric log linear models for simple data sets in which primary interest relates to subject specific comparisons of the repeated responses one can easily obtain the estimates with standard software for log linear models examples include data from crossover designs and from comparisons of treatment and control groups regarding the change between baseline and follow up observations

is the simple carry over model useful it is argued that the models usually employed for carry over effects in cross over trials are not reasonable the example of a non linear dose response for a dose finding trial arranged in a williams square is developed to show that if carry over is present to any appreciable degree the usual statistical models provide no guaranteed protection against its effects it is concluded that the most reasonably defended assumption about carry over effects is that no important carry over has taken place and that where this assumption cannot be defended statistical models provide no satisfactory substitute for it

psychometric functions for gap detection in a yes no procedure to examine models of temporal resolution and to investigate the decision processes underlying the detection of a brief pause in a bandpass noise psychometric functions for gap detection were measured at octave frequencies from 0 25 to 8 khz three normal listeners were tested using a constant stimulus procedure with a cued yes no paradigm the minimum detectable gap mdg estimated from the midpoint of the psychometric functions decreased systematically with increasing frequency the slopes of the psychometric functions generally increased as the test frequency increased up to 2 khz but remained constant at the higher frequencies two models were investigated an energy detector model and a loudness detector model both consisted of auditory filtering a nonlinearity and short term integration in the energy detector model the nonlinearity was a square law in the loudness detector model it was a compressive power law using the usual gaussian approximations the energy detector model fails at low fr

the deterioration of hearing with age frequency selectivity the critical ratio the audiogram and speech threshold the frequency selectivity of the auditory system was measured by masking a sinusoidal signal 0 5 2 0 or 4 0 khz or a filtered speech signal with a wideband noise having a notch or stopband centered on the signal as the notch was widened performance improved for both types of signal but the rate of improvement decreased as the age of the 16 listeners increased from 23 to 75 years indicating a loss in frequency selectivity with age auditory filter shapes derived from the tone in noise data show a that the passband of the filter broadens progressively with age and b that the dynamic range of the filter ages like the audiogram that is the range changes little with age before 55 but beyond this point there is an accelerating rate of loss the speech experiment shows comparable but smaller effects the filter width measurements show that the critical ratio is a poor estimator of frequency selectivity because it confounds the tuning of the system with the efficiency of the signal detection and speech processing mechanisms that follow the filter an alternative one point measure of frequency selectivity which is both sensitive and reliable is developed via the filter shape model of masking

a study of particle swarm optimization particle trajectories particle swarm optimization pso has shown to be an efficient robust and simple optimization algorithm most of the pso studies are empirical with only a few theoretical analyses that concentrate on understanding particle trajectories these theoretical studies concentrate mainly on simplified pso systems this paper overviews current theoretical studies and extend these studies to investigate particle trajectories for general swarms to include the influence of the inertia term the paper also provides a formal proof that each particle converges to a stable point an empirical analysis of multi dimensional stochastic particles is also presented experimental results are provided to support the conclusions drawn from the theoretical findings

a new nonparametric approach for baseline covariate adjustment for two group comparative studies we consider two armed clinical trials in which the response and or the covariates are observed on either a binary ordinal or continuous scale a new general nonparametric np approach for covariate adjustment is presented using the notion of a relative effect to describe treatment effects the relative effect is defined by the probability of observing a higher response in the experimental than in the control arm the notion is invariant under monotone transformations of the data and is therefore especially suitable for ordinal data for a normal or binary distributed response the relative effect is the transformed effect size or the difference of response probability respectively an unbiased and consistent np estimator for the relative effect is presented further we suggest a np procedure for correcting the relative effect for covariate imbalance and random covariate imbalance yielding a consistent estimator for the adjusted relative effect asymptotic theory has been developed to derive test statistics and confidence intervals the test statistic is based on the joint behavior of the estimated relative effect for the response and the covariates it is shown that the test statistic can be used to evaluate the treatment effect in the presence of random covariate imbalance approximations for small sample sizes are considered as well the sampling behavior of the estimator of the adjusted relative effect is examined we also compare the probability of a type i error and the power of our approach to standard covariate adjustment methods by means of a simulation study finally our approach is illustrated on three studies involving ordinal responses and covariates

some analysis strategies for three period changeover designs with two treatments alternative analysis strategies for the three period crossover design with two treatments are discussed in this paper one analysis strategy involves a parametric model that incorporates the effects of interest to implement this method one usually assumes that the covariance structure for the data has the sphericity or circularity property alternative approaches that do not require this assumption are described they are based on the parametric and non parametric analysis of appropriate within subject linear functions of the data the advantage of these methods is that one only needs the assumption that the resulting linear functions for the respective subjects are independent and have a common distribution the parametric approach also requires normality of the resulting within subject linear functions for small sample situations an extension of the non parametric method is considered for cases in which the treatment sequences are randomly assigned within strata the various methods are illustrated for a three period crossover design involving two strata with randomly assigned treatment sequences of the form a b a and b a b

gap detection in normal and hearing impaired listeners temporal resolution estimated by measuring the minimum detectable gap t msec separating two successive signals was assessed in five normal hearing and five cochlear impaired listeners the signals were octave band noises 400 800 hz 800 1600 hz and 2000 4000 hz presented in a background of continuous broadband notched noise that was applied to eliminate unwanted spectral cues temporal resolution in all listeners showed systematic improvement with an increase in octave band center frequency resolution in the hearing impaired subjects was significantly poorer than normal regardless of whether the comparisons were made at equal sound pressure level or at equal sensation level

technical communique static output feedback stabilization an ilmi approach in this note the static output feedback stabilization problem is addressed using the linear matrix inequality technique a necessary and sufficient condition for static output feedback stabilizability for linear time invariant systems is derived in the form of a matrix inequality the extension of the result to h control is studied an iterative lmi ilmi algorithm is proposed to compute the feedback gain numerical examples are employed to demonstrate the effectiveness and the convergence of the algorithm

sentence reception in noise from one versus two sources effects of aging and hearing loss sentence reception thresholds srts and babble detection thresholds bdts were measured for signals presented from loudspeakers located at 0 deg and 90 deg azimuth in addition the s b ratios necessary to achieve srt in the presence of a 12 talker babble were determined under three conditions in which the speech and babble were presented from the same or spatially separated loudspeakers in the first experiment normal hearing subjects were tested on two occasions the results were highly reliable with standard errors of the test retest differences of less than 1db for all conditions in the second experiment srts bdts and s b ratios were measured for three normal hearing groups 39 40 54 and 55 years and for a fourth group with presbycusis 55 years presbycusics had higher srts and bdts than all other groups regardless of age and the oldest normals had higher thresholds than younger subjects presbycusics required higher s b ratios than any of the normal groups and the oldest normal group needed a higher s b ratio compared to the youngest group all groups demonstrated a significant advantage in s b ratio when the sentences and babble sources were spatially separated compared to when they were presented from the same loudspeaker there was no significant difference in the magnitude of advantage due to spatial separation of speech and noise between the normal groups regardless of age but the presbycusics had significantly smaller advantages than all normals these findings suggest that aging alone does not impair the ability to take advantage of the spatial separation of speech and noise and that the speech reception problems of aging individuals involve various components that depend upon the nature of the listening task

generalized linear models with random effects a gibbs sampling approach abstract generalized linear models have unified the approach to regression for a wide variety of discrete continuous and censored response variables that can be assumed to be independent across experimental units in applications such as longitudinal studies genetic studies of families and survey sampling observations may be obtained in clusters responses from the same cluster cannot be assumed to be independent with linear models correlation has been effectively modeled by assuming there are cluster specific random effects that derive from an underlying mixing distribution extensions of generalized linear models to include random effects has thus far been hampered by the need for numerical integration to evaluate likelihoods in this article we cast the generalized linear random effects model in a bayesian framework and use a monte carlo method the gibbs sampler to overcome the current computational limitations the resulting algorithm is flexible to easily accommodate changes in the number

optimal crossover designs in the presence of carryover effects under either the random patient effect model with sequence effects or the fixed patient effect model the usual two period two treatment crossover design ab ba cannot be used to estimate the contrast between direct treatment effects when unequal carryover effects are present if baseline observations are available the design ab ba can validly be used to estimate a treatment contrast however the design ab ba aa bb with baseline observations is more efficient in fact we show that this design is optimal whether or not baseline observations are available for experiments with more than two periods universally optimal designs are found for both models with and without carryover effects it is shown that uncertainty about the presence of carryover effects is of little or no consequence and the addition of baseline observations is of little or no added value for designs with three or more periods however if the experiment is limited to only two periods the investigator pays a heavy penalty

issues for covariance analysis of dichotomous and ordered categorical data from randomized clinical trials and non parametric strategies for addressing them analysis of covariance is an effective method for addressing two considerations for randomized clinical trials one is reduction of variance for estimates of treatment effects and thereby the production of narrower confidence intervals and more powerful statistical tests the other is the clarification of the magnitude of treatment effects through adjustment of corresponding estimates for any random imbalances between the treatment groups with respect to the covariables the statistical basis of covariance analysis can be either non parametric with reliance only on the randomization in the study design or parametric through a statistical model for a postulated sampling process for non parametric methods there are no formal assumptions for how a response variable is related to the covariables but strong correlation between response and covariables is necessary for variance reduction computations for these methods are straightforward through the application of weighted least squares to fit linear models to the differences between treatment groups for the means of the response variable and the covariables jointly with a specification that has null values for the differences that correspond to the covariables moreover such analysis is similarly applicable to dichotomous indicators ranks or integers for ordered categories and continuous measurements since non parametric covariance analysis can have many forms the ones which are planned for a clinical trial need careful specification in its protocol a limitation of non parametric analysis is that it does not directly address the magnitude of treatment effects within subgroups based on the covariables or the homogeneity of such effects for this purpose a statistical model is needed when the response criterion is dichotomous or has ordered categories such a model may have a non linear nature which determines how covariance adjustment modifies results for treatment effects insight concerning such modifications can be gained through their evaluation relative to non parametric counterparts such evaluation usually indicates that alternative ways to compare treatments for a response criterion with adjustment for a set of covariables mutually support the same conclusion about the strength of treatment effects this robustness is noteworthy since the alternative methods for covariance analysis have substantially different rationales and assumptions since findings can differ in important ways across alternative choices for covariables as opposed to methods for covariance adjustment the critical consideration for studies with covariance analyses planned as the primary method for comparing treatments is the specification of the covariables in the protocol or in an amendment or formal plan prior to any unmasking of the study

simulation of the effect of threshold elevation and loudness recruitment combined with reduced frequency selectivity on the intelligibility of speech in noise the effect of loudness recruitment and threshold elevation together with reduced frequency selectivity have been simulated to examine the combined effect of the two major consequences of cochlear hearing loss on the intelligibility of speech in speech shaped noise in experiment 1 four conditions were simulated a moderate flat loss with auditory filters broadened by a factor of three b3r2 a moderate to severe sloping loss with auditory filters broadened by a constant factor of three b3rx and these conditions with linear amplification applied prior to the simulation processing b3r2 b3rx for conditions b3r2 and b3rx performance was markedly worse than for a control condition normal hearing condition r1 tested in a previous study for conditions b3r2 and b3rx linear amplification improved performance considerably however performance remained below that for condition r1 by between 5 and 19 in experiment 2 the broadening of the auditory filters was made more realistic by making it a function of the absolute threshold at the center frequency of the auditory filter three different hearing losses were simulated a moderate to severe sloping loss with variable broadening of the auditory filters bxrx the same moderate to severe sloping loss with linear amplification bxrx and the same broadening of the auditory filters but without the simulation of loudness recruitment and threshold elevation bx for condition bxrx performance was markedly worse than in condition r1 while performance in condition bx was somewhat worse than for condition r1 for condition bxrx linear amplification according to the nal procedure improved performance to a large extent but it remained worse than for condition r1 the results are consistent with previous evidence indicating that only part of the decrease of performance produced by actual cochlear hearing loss can be compensated by conventional linear hearing aids

temporal modulation transfer functions for listeners with real and simulated hearing loss a functional simulation of hearing loss was evaluated in its ability to reproduce the temporal modulation transfer functions tmtfs for nine listeners with mild to profound sensorineural hearing loss each hearing loss was simulated in a group of three age matched normal hearing listeners through spectrally shaped masking noise or a combination of masking noise and multiband expansion tmtfs were measured for both groups of listeners using a broadband noise carrier as a function of modulation rate in the range 2 to 1024 hz the tmtfs were fit with a lowpass filter function that provided estimates of overall modulation depth sensitivity and modulation cutoff frequency although the simulations were capable of accurately reproducing the threshold elevations of the hearing impaired listeners they were not successful in reproducing the tmtfs on average the simulations resulted in lower sensitivity and higher cutoff frequency than were observed in the tmtfs of the hearing impaired listeners discrepancies in performance between listeners with real and simulated hearing loss are possibly related to inaccuracies in the simulation of recruitment

comparisons of frequency selectivity in simultaneous and forward masking for subjects with unilateral cochlear impairments two experiments are described in which frequency selectivity was estimated in simultaneous and forward masking for each ear of subjects with moderate 25 60 db hl unilateral cochlear hearing losses in both experiments the signal level was fixed for a given ear and type of masking simultaneous or forward and the masker level was varied to determine threshold using an adaptive two alternative forced choice procedure in experiment i the masker was a noise with a spectral notch centered at the signal frequency either 1 0 or 1 5 khz threshold was determined as a function of notch width signal levels were chosen so that the noise level required at threshold for a notch width of zero was similar for the normal and impaired ear of each subject in both simultaneous and forward masking the function relating threshold to notch width had a steeper slope for the normal ear than for the impaired ear of each subject for the normal ears these functions were steeper in forward masking than in simultaneous masking this difference was interpreted as resulting from suppression for the impaired ears significant differences in the same direction were observed for three of the five subjects but the differences were smaller in experiment ii psychophysical tuning curves ptcs were determined in the presence of a fixed notched noise centered at the signal frequency 1 0 khz for the normal ears the ptcs were sharper in forward masking than in simultaneous masking for the impaired ears the ptcs were similar in simultaneous and forward masking but those in forward masking tended to be sharper at masker frequencies far removed from the signal frequency overall the results suggest that suppression is reduced but not completely absent in cases of moderate cochlear hearing loss

a tabu search approach for the minimum sum of squares clustering problem in this paper a tabu search based clustering approach called ts clustering is proposed to deal with the minimum sum of squares clustering problem in the ts clustering algorithm five improvement operations and three neighborhood modes are given the improvement operation is used to enhance the clustering solution obtained in the process of iterations and the neighborhood mode is used to create the neighborhood of tabu search the superiority of the proposed method over some known clustering techniques is demonstrated for artificial and real life data sets

temporal resolution in sensorineural hearing impaired listeners temporal masking curves were obtained from 12 normal hearing and 16 hearing impaired listeners using 200 ms 1000 hz pure tone maskers and 20 ms 1000 hz fixed level probe tones for the delay times used here 40 ms temporal masking curves obtained from both groups can be well described by an exponential function with a single level independent time constant for each listener normal hearing listeners demonstrated time constants that ranged between 37 and 67 ms with a mean of 50 ms most hearing impaired listeners with significant hearing loss at the probe frequency demonstrated longer time constants range 58 114 ms than those obtained from normal hearing listeners time constants were found to grow exponentially with hearing loss according to the function 52e0 011 hl when the slope of the growth of masking is unity the longest individual time constant was larger than normal by a factor of 2 3 for a hearing loss of 52 db the steep slopes of the growth of masking functions typically observed

computational methods for parametric lq problems a survey iterative methods for finding the optimal constant feedback gains for parametric lq problems notably for optimal constant output feedback problems are surveyed the connections of several methods to loss function expansions are discussed with important implications to the understanding of their convergence properties especially the descent anderson moore method levine athans like methods and the newton method are considered convergence results are also included the initialization problem and the output feedback stabilization problem are also discussed furthermore it is shown that the concepts and methods surveyed in this paper are useful in solving many realistic generalized parametric lq problems as well notably so called robust parametric lq problems

evolutionary algorithms for optimization problems with uncertainties and hybrid indices many optimization problems in real world applications contain both explicit quantitative and implicit qualitative indices that usually contain uncertain information how to effectively incorporate uncertain information in evolutionary algorithms is one of the most important topics in information science in this paper we study optimization problems with both interval parameters in explicit indices and interval uncertainties in implicit indices to incorporate uncertainty in evolutionary algorithms we construct a mathematical uncertain model of the optimization problem considering the uncertainties of interval objectives and then we transform the model into a precise one by employing the method of interval analysis finally we develop an effective and novel evolutionary optimization algorithm to solve the converted problem by combining traditional genetic algorithms and interactive genetic algorithms the proposed algorithm consists of clustering of a large population according to the distribution of the individuals and estimation of the implicit indices of an individual based on the similarity among individuals in our experiments we apply the proposed algorithm to an interior layout problem a typical optimization problem with both interval parameters in the explicit index and interval uncertainty in the implicit index our experimental results confirm the feasibility and efficiency of the proposed algorithm

pitch discrimination and phase sensitivity in young and elderly subjects and its relationship to frequency selectivity frequency difference limens for pure tones dlfs and for complex tones dlcs were measured for four groups of subjects young normal hearing young hearing impaired elderly with near normal hearing and elderly hearing impaired the auditory filters of the subjects had been measured in earlier experiments using the notched noise method for center frequencies fc of 100 200 400 and 800 hz the dlfs for both impaired groups were higher than for the young normal group at all fc s 50 4000 hz the dlfs at a given fc were generally only weakly correlated with the sharpness of the auditory filter at that fc and some subjects with broad filters had near normal dlfs at low frequencies some subjects in the elderly normal group had very large dlfs at low frequencies in spite of near normal auditory filters these results suggest a partial dissociation of frequency selectivity and frequency discrimination of pure tones the dlcs for the two impaired groups were higher than those for the young normal group at all fundamental frequencies fo tested 50 100 200 and 400 hz the dlcs for the elderly normal group were intermediate at fo 50 hz dlcs for a complex tone containing only low harmonics 1 5 were markedly higher than for complex tones containing higher harmonics for all subject groups suggesting that pitch was conveyed largely by the higher unresolved harmonics for the elderly impaired group and some subjects in the elderly normal group dlcs were larger for a complex tone with lower harmonics 1 12 than for tones without lower harmonics 4 12 and 6 12 for fo s up to 200 hz some elderly normal subjects had markedly larger than normal dlcs in spite of near normal auditory filters the dlcs tended to be larger for complexes with components added in alternating sine cosine phase than for complexes with components added in cosine phase phase effects were significant for all groups but were small for the young normal group the results are not consistent with place based models of the pitch perception of complex tones rather they suggest that pitch is at least partly determined by temporal mechanisms

models for longitudinal data a generalized estimating equation approach this article discusses extensions of generalized linear models for the analysis of longitudinal data two approaches are considered subject specific ss models in which heterogeneity in regression parameters is explicitly modelled and population averaged pa models in which the aggregate response for the population is the focus we use a generalized estimating equation approach to fit both classes of models for discrete and continuous outcomes when the subject specific parameters are assumed to follow a gaussian distribution simple relationships between the pa and ss parameters are available the methods are illustrated with an analysis of data on mother s smoking and children s respiratory disease

design of mixed h2 h control systems using algorithms inspired by the immune system we utilize optimization algorithms inspired by the immune system for treating the mixed h 2 h control problem both precisely known systems and uncertain systems with polytopic uncertainties are investigated for the latter a novel methodology is proposed to compute the worst case norms within the polytope of matrices this methodology consists in defining the worst case norm computation as an implicit optimization problem with a special structure we exploit this structure of the problem for its solution the paper presents both mono and multiobjective optimization algorithms developed from the clonal selection principle the former is the real coded clonal selection algorithm rcsa and the latter is the multiobjective clonal selection algorithm mocsa the complete design process involves the combination of synthesis and analysis the rcsa is used for analysis through the worst case norm computation for a given provided controller the mocsa is used for synthesis working on a population of candidate controllers until providing an estimate of the pareto set for the mixed h 2 h control problem the numerical examples illustrate the power and the validity of the proposed approach for robust control design moreover our approach for worst case norm evaluation is compared with other approaches available in literature

longitudinal data analysis using generalized linear models summary this paper proposes an extension of generalized linear models to the analysis of longitudinal data we introduce a class of estimating equations that give consistent estimates of the regression parameters and of their variance under mild assumptions about the time dependence the estimating equations are derived without specifying the joint distribution of a subject s observations yet they reduce to the score equations for multivariate gaussian outcomes asymptotic theory is presented for the general class of estimators specific cases in which we assume independence m dependence and exchangeable correlation structures from each subject are discussed efficiency of the proposed estimators in two simple situations is considered the approach is closely related to quasi likelih ood some key ironh estimating equation generalized linear model longitudinal data quasi likelihood repeated measures

a log linear model for ordinal data to characterize differential change among treatments we propose a family of log linear models for ordinal data that contain parameters reflecting change patterns to compare treatments relative to change from baseline under the most general model rates of change can depend not only upon the direction of change but also upon the level of the baseline classification we describe methods for selection of a parsimonious model and for tests of hypotheses concerning treatment differences interpretation of treatment differences in the follow up response profiles within baseline strata employs the concept of stochastic ordering data from two clinical trials illustrate the proposed procedure