bluuebunny/crossref_metadata_2025 huggingface dataset:
Van ziektegeval tot ziektengetal*
Authors: de Groot J. W.
Published: April 2008

This article contains a discussion of the various problems the epidemiologist meets in measuring morbidity; both, at the beginning, in defining the counting units, and at the end, in interpreting the results. The author stresses that most of our knowledge about the distribution of morbidity and the patterns of disease is still lacking. An exception should be made for statistics of absence in industry. However, by using this medium new problems are introduced by the divergency of absence behaviour. The author indicates that the influence of these behaviour governing factors can be eliminated by converting the incidence rates into proportionate figures. With this simple procedure comparability of contemporary absence data can largely be increased. As to previous periods, for some diseases at least, comparison will still be hampered by changes in health conception. A striking example of altered attitudes in this respect procures “neurosis”.
A note on the fitting of certain types of experimental data*
Authors: Wynn P.
Published: April 2008

This paper is concerned with the problem of determining those values of the parameters Z, Aiαi (i = 1, 2, …, h) which provide a best fit of the form

to the observed values fs= f(ts) (s = 1, 2, …, n) in the sense that the sum is a minimum.

Two iterative numerical techniques for the solution of this problem are discussed. The first, a variable gradient method, converges rapidly but involves a relatively large amount of computation; the second involves less computation but converges less rapidly. It is shown that by application of a suitable acceleration technique to the second method, its convergence is made as rapid as that of the first.

Samenvatting

Dit artikel behandelt het probleem der bepaling van die waarden der parameters Z, Ai, αi (i = 1, 2,…, h), die de beste benadering geven van de vorm

aan de waargenomen waarden fs= f(ts) (s = 1, 2, …, n) in die zin, dat de som een minimum is.

Twee iteratief numerieke technieken voor de oplossing van dit probleem worden besproken. De eerste, een variabele gradient methode, convergeert snel, doch houdt een relatief groot aantal berekeningen in; de tweede houdt minder berekeningen in, doch con vergeert minder snel. Er wordt aangetoond dat, by toepassing van een geschikte versnellingstechniek by de tweede methode, de convergentie even snel is als die der eerste.
Note on unbiased estimation of the squared multiple correlation coefficient
Authors: Barten A. P.
Published: April 2008

Samenvatting

Zoals bekend is het kwadraat van de correlatie‐coëfficiënt bij regressie‐analyse een onzuivere schatting van zijn tegenhanger in de populatie. Deze onzuiverheid wordt afgeleid tot op de orde 1/T, waarbij T het aantal waarnemingen is. Door een schatting van deze onzuiverheid van het kwadraat van de gewone correlatie‐coëfficiënt af te trekken wordt een nieuwe schatting van de correlatie in de populatie verkregen, die zuiver is tot op de orde 1/T, hetgeen van de op de gebruikelgke wijzen gecorrigeerde correlatie‐coëfficiënten niet gezegd kan worden.
Statistical testing of the accuracy of forecasts
Authors: Nagar A. L.
Published: April 2008

Samenvatting

In dit artikel wordt een toets ontwikkeld om de nauwkeurigheid van voorspellingen te onderzoeken. Als toetsingsgrootheid wordt gebruikt waarin A1… An waargenomen waarden en P1… Pn voorspellingen van dezelfde reeks stochastische variabelen zijn. Onder bepaalde veronderstellingen benaderen we de verdeling van ϕ door eengammaverdeling. Als illustratie passen we deze toets toe op de volgens de conjunctuurtoets verkregen voorspellingen, met betrekking tot firma's in de Duitse leer‐ en schoenen‐industrie.
The design of optimal committee decisions*),**)
Authors: van den Bogaard P. J. M. , Versluis J.
Published: April 2008

Samenvatting

Het uitgangspunt van dit artikel is een commissie van N personen, die tot taak heeft een beslissing te nemen op basis van de voorkeuren van zijn leden. Deze voorkeuren worden weergegeven door voorkeursfuncties, die eenduidig verondersteld worden afgezien van een willekeurig nulpunt en eenheid. De gevolgde procedure houdt in, dat een commissievoorkeursfunctie word geconstrueerd, die een lineaire combinatie is van alle individuele voorkeursfuncties. De gewichten van deze lineaire combinatie worden afgeleid uit de zogenaamde verliezenmatrix, waarvan elk element aangeeft het verlies (d.i. de reductie beneden het bereikbare voorkeurmaximum), dat een commissielid i lijdt wanneer een comissielid j erin slaagt zijn wil aan de commissie op te leggen. In beginsel wordt aanbevolen de verliezenmatrix symmetrisch te maken, hetgeen dan leidt tot eenduidige gewichten van de genoemde lineaire combinatie en dus tot een eenduidige cornmissievoorkeursfunctie. Dit beginsel kan echter niet altijd worden gerealiseerd; aanbevolen wordt dan de rijsommen van de verliezenmatrix gelijk te maken aan de corrresponderende kolomsommen. Deze gedachtengang wordt toegepast op de voorkeuren van drie groepen van de Sociaal‐Economische Raad (werknemers‐, kroon‐ en werkpeversleden) t.a.v. de economische situatie in 1957.
Door meten tot weten in de sociale wetenschappen*)
Authors: de Wolff P.
Published: April 2008

Knowledge by measurement in the social sciences, address to the general meeting of the Netherlands Statistical Society.

The motto “Knowledge by measurement” of the great Dutch physicist Kamerlingh Onnes is also valid in the social sciences. Knowledge about economic and social phenomena must be obtained to a large extent by measuring quantities, ratios, mutual relations and growth factors.

During the past 20 years a considerable progress is made in this field, which is shown by two examples.

In a certain sense the motto mentioned above is a euphemism: however much our measurements may be improved, our knowledge remains incomplete. The observation of social phenomena is unique, they cannot be reproduced and the research worker meets different kinds of restrictions in practical experience. A careful criticism of the results of experimental research is all the more necessary, particularly in the case that these results have to be used as a tool for general economic planning.
Some numerical results on waiting‐time distributions for dependent arrival‐intervals*)
Authors: Runnenburg J. Th.
Published: April 2008

Samenvatting

Ter illustratie van een elders beschreven theorie worden hier voor een één‐loket wachttijdprobleem enige numerieke resultaten gegeven en besproken. Hieruit blijkt, hoe de wachttijdverdeling (althans in het hier beschouwde geval) variëert met de afhankelijkheid der aankomstintervallen.
Samenvatting van het artikel “Procesnauwkeurig heid en toleranties”*)
Authors: Gelling H. , Schaafsma A. H.
Published: April 2008

Summary of a lecture held at the “Statistische Dag 1962”, The Hague. The complete text of this lecture has been published in Sigma 8 (1962), no. 2, p. 26.
Weten in aansluiting op een variantie‐analyse*)
Authors: Keuls M.
Published: April 2008

Too often an analysis of variance is simply completed by afinal F‐test. Although most textbooks do not give sofar the full range of decision procedures that have been presented, practice has reached the point that a greater variation of techniques for formulating conclusions is asked for. No such procedure should be considered loose from its power (in a wider sense), it being expressed as an operations characteristic or in some other way. This paper discusses in a schematic way some decision procedures and gives references for details.
Een sectormodel van het energieverbruik*)
Authors: Middelhoek A. J.
Published: April 2008

The energy model described here serves mainly for planning on long term. The analysis is performed in two stages, of which the first is related to final consumption, and the second stage to the consumption of energy in the conversion sectors. The model of final demand for energy consists of a number of sub‐models, one for each consumption sector. Each sub‐model comprises one equation relating total consumption of useful energy to the relevant indices of activity, and some relations describing the substitution between various forms of energie. Only in this way the various trends in the consumption of the different forms of energy can be taken into account. Given the future value of total useful consumption by sector and the consumption patterns, the future final consumption by form of energy can be found. After that we can start with the second stage of the model, which has been formulated as an input‐output model. Given final demand for energy, which equals national consumption on the final level minus net imports of the form of energy concerned, and the matrix of energy input coefficients for the conversion sectors, total production and consumption of energy can be calculated.
Een systeem van kostenbeheersende productieplanning
Authors: van der Sloot J. de Boer en J.
Published: April 2008

In this paper a system of cost‐controlled production planning is described. This system considers all kinds of costs associated with a production in phases (e.g. production of units, production of subassemblies, assembly) which may be affected by the planning, such as set‐up costs, costs of transport, control, inventories, capacity and changes in capacity.

The mathematical model leads to a linear or mixed discrete‐linear programming problem whose solution gives for each time period considered the size of the capacities which should be used and of the series of different products which should be produced. Practical recommendations are given for obtaining a sufficiently satisfying solution.
Het bepalen van bestelniveaus wanneer afname en levertijd gamma‐verdeeld resp. normaal‐verdeeld zijn
Authors: Moonen H. J. M.
Published: April 2008

In studies of inventory control problems in industry it is often supposed that there is a variable demand and a constant delivery time.

This assumption is rarely tenable. In this paper rules are developed for determining the reorder level when the demand has a gamma distribution and the delivery time is normally distributed.
De Computer: Werkwijze en toepassingsmogelijkheden van elektronische rekenmachines
Authors: van de Bosch J. P.
Published: April 2008

Since world‐war II, there has been an enormous development in the field of the electronic data processing equipment.

This rapid development was on one side due to the boom which followed the war, on the other hand the armaments‐race contributed considerably to a further increase of the research in this sector.

In the years 1948–50 it became clear that this equipment could also be of great advantage in other areas than scientific, such as business administration, automatic translation, information retrieval and production control. These applications, however, made other demands on the computer. A greater and faster memory and more speed in input and output of data were necessary. The research in the last few years is therefore mainly concentrated on these problems.

The computers, as they are now available, consist of 5 units: input device, calculating‐unit, storage, control unit and output device. The processing is controlled by means of a program, which consists of a number of instructions, prescribing in detail the operations to be performed by the machine.

It will be clear that the use of this equipment requires a careful study beforehand, whilst also the implications on staff and organisation must be considered.
Planning the maintenance of simple machinery
Authors: Heiden J. A. v. d.
Published: April 2008

Samenvatting

In het artikel is een methode beschreven voor het berekenen van de optimale tijden, waarop preventief onderhoud van apparatuur, instrumenten en machines dient te geschieden, indien deze apparatuur, enz. zich na dit preventief onderhoud zowel als na een reparatie tengevolge van een storing gedraagt alsof ze nieuw is. Gemakshalve is dit type apparatuur in de titel “simple machinery” genoemd.

In het eerste deel (paragraaf 1 en 2) wordt beschreven hoe deze optimum tijden afgelezen kunnen worden uit een aantal grafieken. Het tweede deel (paragraaf 3 t/m 9) geeft de theorie en enige additionele informatie, die verkregen kan worden door het uitvoeren van enige eenvoudige berekeningen. Deze informatie maakt het mogelijk de kosten van reparaties, preventief onderhoud, enz. en het verlies van produktieve tijd tussen een machine, waarvan het preventief onderhoudsschema optimaal is te vergelijken met dat van een machine met niet optimaal berekend onderhoudsschema.

Doordat de oorspronkelijke theorie, afkomstig van Morse [1], door de wijze van benadering en afleiding, gegeven in dit artikel eenvoudiger toegankelijk ge‐worden is, kan nu in de olie‐industrie worden nagegaan, welke onderhoudsschema's verbeterd kunnen worden. Hierbij wordt in gedachten gehouden, dat de theorie slechts toepasbaar is op die apparatuur, die voldoet aan bovenstaande “simple machinery” definitie.

De Appendix geeft de wiskundige afieidingen, gebruikt in het artikel.
Gissen en beslissen met historische gegevens*
Authors: Oppers V. M.
Published: April 2008

Since the beginning of this century an almost uninterrupted flow of publications has drawn attention to the ever growing average height of man in the Western Hemisphere. It was said that the lengthening found during youth had already resulted in an adult height averaging over 15 centimeters (= 6“) taller than 100 ytars ago.

This study is aimed at proving that, for a great part, the fixation of the growing height of adult man has, so far, been founded on an error, which, peculiarly enough, has come into being in an identical way in all countries where publications on this subject have appeared. After having been convinced of this error it has been possible to reveal a number of characteristics of the growth of man, unknown so far.
Beslissen zonder (ver)gissen bij de keuze van een toets*
Authors: de Jonge H.
Published: April 2008

For a number of simple but frequently occurring designs the relations are studied between five types of statistical tests, e.i. (1) ‘classical’t‐ and F‐tests, (2) permutation tests, (3) rank tests, (4) tests for dichotomies, (5) χ2‐tests for categorical systems. On the ground of the relations between these types of tests directives are given for the choice of a suitable test, based on (a) the kind of design, and (b) a classification of observations which is easy in operation.
Een permutatietoets voor alternatief verdeelde groot‐heden*
Authors: van Elteren Ph.
Published: April 2008

A permutation test for random variables that assume the values 0 or 1 only (read for the meeting of the Netherlands Statistical Society in 1963).

Consider a matrix of stochastically independent random elements xαi (α= lm; i = In) with

P[xαi= 1] = 1‐P[xαi= 0] = pαi

A permutation test is proposed for the hypothesis H0: pα2=pα2=pαn (α= lm). The statistic of the test is given by the formulas (1.1) and (1.2), its critical region by (1.3). It is shown that this test can be considered as a special case of the method of m rankings of M. Friedman (cf literature [1]) and of a similar test of A. S. C. Ehrenberg (cf [3], [4], [5]). Exact distribution functions (under H0) are tabulated for some special cases (tables 1, 2, 3, 4) and approximations are proposed based on limit theorems for m→∞ (χ2‐distribution) for n→∞ (normal distribution) and on fitting of mean, variance and range (F‐distribution). A consistency theorem is derived for the cases m constant, n→∞ and n constant, m→∞.
Verschillen in doeltreffendheid tussen groepen van voor‐spellende variabelen*
Authors: Corsten L C. A.
Published: April 2008

A test of significance for differences in efficiency among several sets of predictors of a predictand is proposed. The difficulties in posing the problem are explained.
Smoothing Sales Data by Progressive Correction
Authors: van Dobben de Bruyn C. S.
Published: April 2008

Samenvatting

Het vloeiend volgen van verkoopcijfers door Progressieve Correctie.

Met een analogie tussen het vloeiend volgen ‐ soms voorspellen genoemd ‐ van een reeks verkoopcijfers en het automatisch regelen van een fysisch proces als leidraad wordt een nieuwe methode voor dit volgen getoond. De hieraan gegeven naam is: Volgen door Progressieve Correctie. De positie van deze methode t.o.v. “Exponential Smoothing” en de kwaliteitscontrole wordt aangeduid.
A different solution of a problem posed by Theil and Schweitzer
Authors: Corsten L C. A.
Published: April 2008

Samenvatting

De vraag naar de nauwkeurigste (d.i. kleinste tweede moment) schatter van de restvariantie a2 bij lineaire regressieanalyse met isomore onafhankelijke normaal verdeelde residuen wordt opnieuw beantwoord, maar longs vrijwel geheel andere weg dan door THEIL en SCHWEITZER [3] bewandeld. Het blijkt bovendien dat deling van de residuele som van kwadraten door het bijbehorende aantal vrijheids‐graden + 2 niet alleen in de klasse der kwadratische funk ties der waarnemingen maar zelfs in de klasse van alle veelvouden van zuivere schattingen van σ2 de nauwkeurigste is. Gebruik wordt gemaakt van de in een appendix bewezen stelling, dat de traditionele schatter van σ2, waarbij de residuele som van kwadraten door het bijbehorend aantal vrijheidsgraden wordt gedeeld, de nauwkeurigste is onder alle zuivere schatters.
Tijdreeksen en regionale jaarrekeningen
Authors: Venekamp P. E.
Published: April 2008

Since some acquaintance with the development of economic aggregates with regard to the town of Amsterdam is needed, the Municipal Bureau of Statistics calculated some of these quantities during the period 1953–1960. The data derived from the Social Accounts 1953 of the city of Amsterdam were taken as a starting point for the calculations. The present article has been Written to show the principles of construction.
Programmering van de woningbouw in verband met de woningkwaliteit*
Authors: Sittig J.
Published: April 2008

Programming the production of dwellings in the Netherlands

Programming for a year the building of dwellings in the Netherlands is treated by linear programming. Restrictions are introduced for man‐power, material, private capital, subsidies and foreign currency.

A “program” consists of two numbers, S (number of dwellings to be built with governmental subsidies) and V (number of dwellings to be built in the free market).

The objective is discussed at length. With the returning to normal conditions in building, S‐dwellings will be subject to a higher rate of depreciation than V‐dwell‐ings.

A purely quantitative objective for the program is rejected in favour of a qualitative one: maximizing the value which the dwellings built in this year will possess, say, in 1975.

A simple graphical solution is shown, and the effect on the program of the industrialization of building is discussed.
Modellen*
Authors: Leppink G. J.
Published: April 2008

Inaugural address at Utrecht university. The subject is the use of models in statistical research.

Mevrouw en Mijne Heren Curatoren,

Mijnheer de Rector Magnificus,

Dames en Heren Hoogleraren, Lectoren, Docenten en overige Leden van de

Wetenschappelijke Staf,

Dames en Heren Studenten,

en voorts Gij alien, die door Uw aanwezigheid van Uw belangstelling blijk geeft,

Zeer gewaardeerde Toehoorders,
Signaalstroomdiagrammen en Markov‐ketens
Authors: Bakker W.
Published: April 2008

The transient behavior of a simple two‐state discrete Markov process can be studied by means of matrix‐multiplication and z‐transformations.

For linear systems the output is equal to the convolution of the input and the impulse response of the system. By taking z‐transforms the convolution can be avoided: the transform of the output is equal to the transform of the input multiplied by the transform of the impulse response of the system.

The signal flow graph method is the transformation of the matrix‐method of solving a system of simultaneous equations in a topological method.

The simple two‐state discrete Markov process can be represented by such a flow graph and it is shown how to simplify this flow graph step by step. Taking as input the unit‐impulse at time zero, the output of this system at time n turns out to be the n‐step transition‐probability.

The results for the transmission in a network are mentioned (Mason and Zimmermann [8]). With these results it is possible to give at once the n‐step transition probability of a system without first simplifying the flow graph.

Building on this result signal flow graphs can be used to determine the chance to be for the first time in a certain state, the average number of times a system is in a certain state and the chance to reach a certain state for the first time before another state of the system has been reached.

Finally the results are extended to continuous Markov processes.
Enkele stochastische eigenschappen van een uit vezels ge‐sponnen garen voor het ideale klassieke spinproces en enkele ermee samenhangende problemen
Authors: Terpstra T. J.
Published: April 2008

Some stochastic properties of a yarn spun from fibres for the ideal classic spinning process and some connected problems.

For the ideal classic spinning process {for definition cfi section 2) the characteristic functions of the cross‐section of a yarn and the volume of a yarn‐piece are derived. It is assumed that the fibres possess a two‐dimensional probability distribution for their length and cross‐section, however with the restriction that the fibre‐length has an upper bound with probability one.

For the case that the fibres have uniform cross‐section the spectral functions of the foregoing quantities are given.

Under the same condition of a uniform cross‐section of the fibres analogous results have been obtained by H. BRENY [7], however in quite another and partly more tedious way. The spectral function of the yarn‐cross‐section has also been independently obtained by KIYOHISA FUJINO and SUEO KAWABATA [8].

In spinning practice the coefficient of variation of the yarn‐cross‐section for the ideal classic spinning process {the so called coefficient of MARTINDALE) is denoted an optimal character in so far as it should be the minimum coefficient of variation, which is attainable. This is certainly the case if the disturbances in the spinning process are independent of the irregularities already contained by the yarn.

However, if the disturbances are dependent on the yarn‐irregularity, then it is a priori not sure that the irregularity will always increase. Perhaps the opposite may occur.

In this connection it seems an interesting problem to determine the implications on the yarn irregularity by using servo‐mechanisms in the spinning process. Some investigations in this direction have already been done by the Japanese (cf. the references).
Internationaal Marktonderzoek*
Authors: Emanuel H.
Published: April 2008

In this article the autor considers the problem specific to international market research ‐ defined as any project of market research which entails subprojects in different countries that have to produce results in a certain harmony ‐ mainly as that of coordination. He restricts himself to primary research, especially based on interviewing. To serve the purpose of harmony design and execution of national sub‐projects of research must differ because of two sets of factors which are described in some detail: a. national socio‐cultural infrastructures are different b. researchers and collaborators act from a different mental pattern in different countries. The type of coördination which is needed is exemplified from experiences obtained with research in the Netherlands and Belgium. The following aspects of survey‐research are discussed in this respect: the interviewer (supply, selection, training, control), the questionnaire, sampling, the researcher and his surroundings.
Taalstatistiek*
Authors: Corstius H. Brandt
Published: April 2008

Discussion of the possibilities and limitations of Language Statistics.

Sampling of “normaI” prose is difficult as the “universe of written Dutch” is undefined. What predictions can be made about the contents of tomorrow's newspaper? The letter frequencies are very stable. Frequencies ofbigrams and trigrams of letters bring us towards the word level about which something may be predicted. The sentence level can only be dealt with after a mechanical sentence analysis method is available. The highest level is still outside the scientific domain and belongs to the literary critic. Literary Statistics should be founded on a solid knowledge of Language Statistics. It is considered inappropriate to begin this field with difficult historical problems. The mutual distrust between linguist and statistician requires much tact on both sides. Eventually Language Statistics may become one of the bridges between the “two cultures”. The modern computer is an indispensable tool both for practical reasons (the giant mass of material) and for theoretical ones (the need to give unambiguous definitions of concepts like “sentence”, “word” and “syliable”). The use of Language Statistics in Mechanical Translation research is discussed. Review of the activities in the Netherlands. A one million word count is on its way. The speaker pleads for a National Center for Lexicology and Language Statistics.
Statistiek en verkeer*
Authors: Volmuller J.
Published: April 2008

Statistics and traffic.

Traffic defined as the collectivity of moving (andparked) vehicles, is the direct consequence of transportation needs as they occur in society as a result of economic and social activities. Hindrances to the free flow of traffic result in decrease and even stagnance of human activities. The correct functioning of traffic facilities is imperative to modern human society.

To solve traffic engineering problems, present and future traffic loads must be determined and traffic behaviour in relation to geometric road design must be known. As the volume and character of human activity fluctuates and changes in time, traffic loads will vary in volume and character. Any parameter used to indicate traffic load (volume, speed, etc.) has no well determined value but rather should be evaluated by describing its frequency distribution (histogram). The traffic engineer should not design for the average value, because the facility would not render the expected services whenever a value higher than average would occur. Nor should he design for the highest value, because then the facility will be underloaded, and therefore uneconomical, except when this exceptionally high value occurs. This is illustrated in case of determining the “design speed” for a curve in a road and of determining the “design‐volume” for a road‐crosssection.

To determine the histograms of the various design‐factors numerous observations of actual traffic are required. The survey programs should be well correlated with the data which are required for designwork to limit scope and cost. Often, sampling will render data of sufficient accuracy; the required accuracy being set by the design engineer. The statistician will render essential services in determining the size of samples, the survey programs and supervising the correct processing of data.

The statistical problems involved in traffic‐behaviour research work are even more challenging because many of the factors involved are not known and should be detected through large series of observations.
Communication between the experimental animal and the pharmacologist*
Authors: van Noordwijk J.
Published: April 2008

Samenvatting

De meeste farmacologen gebruiken het dier als model voor de mens. Hoewel goede registratietechnieken thans rechtstreeks farmacologisch onderzoek bij de mens in veel meer gevallen mogelijk maken dan bij het ontstaan van de experi‐mentele farmacologie in de 19e eeuw, blijft het noodzakelijk, zoveel mogelijk informatie over de farmacologische werking van een stof in dierproeven te ver‐zamelen, voordat deze voor de eerste keer aan mensen toegediend wordt.

Soms trekt de farmacoloog uit de informatie welke de dierproef leverde ver‐keerde conclusies. Voor kwalitatief verschil in werking bij mens en dier bestaat achteraf vaak een bevredigende verklaring, welke gebruikt kan worden om de voorspellende werking van toekomstige dierproeven te vergroten. De mogelijkheid om uit dierproeven bijwerkingen bij de mens te voorspellen is categorisch beperkt; met deze beperkingen blijkt de dierproef toch nuttige informatie te kunnen leveren.

Onderzoek van de regressie van de log dosis op log lichaamsgewicht laat zien, dat er tussen de werkzame dosis voor dier en mens (M.M. geldt dit ook voor de toxische dosis) een duidelijker verband bestaat dan meestal aangenomen wordt.
Communicatie en medische statistiek*
Authors: Riimke L.
Published: April 2008

Communication and Medical Statistics

Statistical methods can contribute to a good communication between medical research workers. This is demonstrated with examples, chosen from the fields of health statistics, pharmaceutical research and clinical chemistry.
De “car‐following law”*
Authors: Kamphorst H.
Published: April 2008

The car‐following law tries to describe the behaviour of a number of cars who are forced to drive in a line. This law and the derivation of stability limits for the propagation of disturbances along a line of cars will be discussed.
Een kort overzicht van codes die tegen foutenuitbarsting bestand zijn*
Authors: Gross Alan J.
Published: April 2008

When information is transmitted over a channel errors often occur in bursts, usually due to the presence of some disturbance in the channel for a short period of time. Thus, it is possible that a single burst of two or three errors occurs somewhere in the message whereas the remainder of the message is error‐free.

In this article we discuss only binary burst‐error‐correcting codes. We introduce the work of HAMMING, ABRAMSON, BOSE and CHAKRA VARTI, and GROSS all of whom have constructed burst‐error‐correcting codes, and whose codes are capable of correcting single bursts of errors of length less than or equal to four.
Prognose van het autopark met behulp van een “diffusion”‐model*
Authors: Vemtetten J. B.
Published: April 2008

In a diffusion‐model the distribution of purchases of a good over different income classes forms the starting point of analysis. For luxuries the distribution function is continuously increasing. In this case increasing incomes will always lead to a greater demand or a greater stock of the good. Moreover, the function as a whole will shift to lower income classes for goods for which the consumer's acceptance is not yet complete. This causes an autonomous increase of the demand over time; an increase which is not dependent on the rise of income. The lack of data, however, restricts the possibility of using the model. Under certain conditions transformation of the model into a form suited for time‐series analysis, is possible. In this form the model has been applied to the stock of motor‐cars, which are in use by families. From this analysis forecasts of the number of motor‐cars for 1970 and 1980 have been computed.
Scaling metoden bij konsumenten‐ondenoek*
Authors: van Westendorp P. H.
Published: April 2008

As psychological market research develops more and more attention will be paid to the research techniques developed in the social sciences. The application of scaling techniques for attitude‐scaling and word‐association‐rating in the frame of large‐scale sample surveys can yield meaningful results for marketing, especially if more powerful techniques of analysis, like factor‐analysis are applied. In this article the major techniques of attitude‐ and wordassociation‐scaling are briefly outlined. It is stated, that method of summated scores (Likert ‐ analysis) for attitude‐scaling combines reasonable discriminative power with a non ‐prohibitive outlay in time and money.
Verkeerskunde als toegepaste wetenschap*
Authors: Jacobsen L H.
Published: April 2008

This paper gives some thoughts about the situation of traffic engineering among other branches of human knowledge.

There are many links as well with forms of human knowledge as well as with the sciences.

Traffic and traffic engineering are influenced from many sides resulting in a situation which as a whole cannot be regarded as acceptable up till now.

Traffic engineering which is not a new form of knowledge, will influence our way of living a good deal. The danger exists that partial knowledge in this field is regarded as the complete knowledge which should rule our decisions in this field of human activities.
De communicatie van nieuwe landbouwmethoden*
Authors: van den Ban A. W.
Published: April 2008

In order to increase the effectiveness of the agricultural extension service a study has been made of the way new farm practices are communicated to the farmers. This paper discusses some statistical problems which arose in that study, especially the construction of a scale for the measurement of the adoption of new practices by the farmers, and some scales for the influence which each farmer has among his colleagues, the use of tests of significance and the analysis of the relationship between different variables by factor analysis. In addition the possibility to stimulate communication processes is mentioned.
Naar aseptische en realistische methoden in de toegepaste statistiek
Authors: Goudriaan J.
Published: April 2008

Summary

Applied statistics is not pure mathematics but the application of suitable methods of mathematical statistics to practical problems.

In choosing the method one should be extremely suspicious in regard to septic methods and give strong preference to realistic methods.

Septic methods are those which by their very nature introduce properties alien to the magnitudes concerned e.g. addition of non‐additive variables, differentiation of stochastic variables, stochastic treatment of indeterminate variables, etc. Realistic methods are those based on a preliminary analysis of the practical problem which should bring to light the essential mutually independent variables controlling the outcome of the problem. Undue simplification at the cost of the accuracy required in actual practice should be avoided; especially weak correlations between variables shown by the deductive analysis as being essentially mutually independent should be discarded.

On the other hand the mathematical treatment should be as simple and direct as possible.

The professional mathematician can become a real danger if he wants to guide the application of mathematical statistics to certain fields of applied science in which he is not sufficiently specialised and experienced. Contrariwise, if he acquires this knowledge in business, the highest positions are open to him.
Price determination based on quality An Application of Minimax
Authors: Boot J. C. G.
Published: April 2008

Samenvatting

Het komt dikwijh voor dat een partij goederen van eigenaar wisselt zonder dat hetzij koper hetzij verkoper de kwaliteit ervan precies kennen. In dergelijke ge‐vallen wordt de prijs gewoonlijk vastgesteld op basis van een door arbitrage be‐paalde kwaliteit. Het in dit artikel te bespreken contract werd in de Rotterdamse haven afgesloten tussen een koper en een verkoper die geregeldpartijen van elkaar overnamen met het doel te bezuinigen op arbitragekosten en tijd. Zij trachtten dit te bereiken door het onderling eens te worden over de kwaliteit volgens van te voren contractueel vastgelegde “spelregels”.

Het resulterende “spel” kan met behulp van de minimax redenering worden opgelost ‐ en vormt als zodanig een der zeer weinige voorbeelden van een praktijk‐voorbeeld van speltheorie. De spelregels hidden echter niet tot het gewenste resultaat, en men gaat nu weer met de alouds vertrouwde orthodoxe arbitrage te werk.
Inleiding in de techniek van elektronische rekenautomaten*
Authors: van der Poel W. L
Published: April 2008

An introduction is given into the most important concepts and terms of computers. Basic constructions, storage, arithmetic units, control, input and output, levels of storage, speeds. Modern concepts, multiprogramming, concurrent programming. The importance of software is stressed and a few examples of programming languages are given. Fortran, ALGOL, LISP.
Optimale instelling van een pakmachine met behulp van simulatie op een computer*
Authors: Doornbos R.
Published: April 2008

Powdered synthetic detergents are packed on machines which work with volumetric proportioning. The bulk density of the powder varies to such an extent, however, that conventional weight control methods are not applicable.

There are machines which automatically adjust the volume of the filling mechanism in reference to one or more weighings of packets. The packets are weighed at a certain frequency. The range between the control limits, the number of times the limits are exceeded to which is reacted and the extent of correction are adjustable.

As determination of the optimum setting by analysis was not feasible a solution was found by simulation on a computer.

The model chosen for the weights of the successive packets was a MARKOV process because this provides a pattern which very closely resembles practical conditions.
Ervaringen met een computer in de Medische Statistiek*
Authors: Rurnke Chr. L
Published: April 2008

Experiences with a computer in Medical Statistics

Application of mathematical statistics to biomedical problems is facilitated by the use of a computer. When choosing a design the amount of calculation need not be taken into account.

As an example the course of the procedure is described for an analysis of variance performed upon the data from a pharmacological experiment according to a 2 < 2 < 3 factorial design.
Overzicht van ontmengingsmethoden voor twee normale verdelingen*
Authors: Motenaar W.
Published: April 2008

The parameters of a mixture of two normal distributions can be estimated in several ways from a sample of grouped observations. Various methods, already known in the literature, are listed and compared.

After an introduction and a statement of the problem, moment estimators, graphical methods and maximum likelihood estimators are mentioned. Some remarks are made on the advantages of the various methods, and on classification. The results of the methods are compared in five representative examples of mixtures.
Monte Carlo estimation of the powers of the distribution‐free two‐sample tests of Wilcoxon, van der Waerden and Terry and comparison of these powers*
Authors: van der Laan P. , Oosterhoff J.
Published: April 2008

This paper describes a method for determining the power functions of the distribution‐free two‐sample tests of WILCOXON, VAN DER WAERDEN and TERRY by a simulation technique, and for comparing these tests with each other and with parametric tests. For samples of size 6 and normal shift alternatives the numerical results are reproduced.
Extrapolatie van tijdreeksen*
Authors: Vos J. W. E.
Published: April 2008

Extrapolation of time‐series.

In this paper only singular stationary stochastic processes are considered, which means that the error variance in predicting the future may be made indefinitely small. From the point of view of the spectral distribution function there are various types of singular processes. Likewise a classification of singular processes may be made by the form of the prediction formula and by the way the prediction error tends to zero. An attempt to find a correspondence between these classifications is made.
Het gebruik van computers bij econometrisch onderzoek*
Authors: Cramer J. S.
Published: April 2008

Computers permit data‐processing on a large scale, and more important, admit of the automatic control of the computing process on the basis of intermediate results. Econometric research stands to benefit largely from the first facility as there is a large volume of micro‐economic data that has hitherto remained unused. It is doubtful, however, whether econometrics can as yet make full use of the second possibility; much of it is of an experimental character and demands frequent decisions based on the judgement of the research worker. At present the main need is for research workers to exploit the computational facilities rather than for computing capacity in itself.
Voorraadbeheer en computer*
Authors: van Ham Ir. C. J. G. J.
Published: April 2008

Both in the design of a stock control system and in the routine performance of this system, a computer can be used. A case study concerning stock control of fasteners destined for assembling and maintenance departments will illustrate some possibilities and limitations in the use of a computer. Particular attention will be paid to the exponential smoothing method which has for object the extrapolation of time series, such as sequences of demand figures.
Change‐over“‐proeven*
Authors: Verdooren L R.
Published: April 2008

The use of change‐over trials is discussed. The principles of analysis are given for change‐over trials with residual effects persisting one period.
Een analyse van grondwaterstanden die beïnvloed worden door de getijdebeweging*
Authors: Stol Ir. Ph. Th.
Published: April 2008

In hydrology and water management research knowledge of the cause of changes in groundwater levels often is of great importance. Changes of ground‐waterlevel can be caused by precipitation and evaporation, by positive ‐ or negative seepage, by polder‐discharge and local discharges for industrial needs: along tidal‐rivers also by the influence of the tides. The effect of the tide (R) and of local discharges (P) together, give several types of groundwater level‐curves (Jig. 2). The propagation of the tide takes place with a shift in phase (tt in (I)) and a damping of the amplitude (fig. 6). To determine in an empirical way the rate with which the phase shifts, in connection with the distance (x)from the banks of the river, a simple regression model (2) is recalculated several times, shifting mutually the series of data before each calculation. This work can easily be done by means of a computer, loading in sequence the data of the test‐wells (W) located in the region under discussion (fig. I). That shift which results in the highest multiple correlation‐coefficient is used to determine the difference in phase with reference to the tide present in the river (table 1, giving the effect of increasing phase shift (tB) on the correlation coefficients, with in the columns: phase shift in hours; mult. corr. coeff.; time in degrees; corr. with river level). The results, for instance the numerical values of the correlation between each test well and the river, critical values of deviations from the model, the regression coeff. (b2) for local effects, are represented in maps (Jig. 3, 4, 5), and may serve to determine the magnitude of soil‐physical constants.
Simulatie van Leerprocessen: geprogrammeerde experimenten; een experimenteel programma*
Authors: Dirkzwoger A.
Published: April 2008

Human verbal learning is considered as an interaction between two information‐processing systems (e.g. the teacher and his pupil) by which one or both are modified. We discussed the possibilities of using a computer program to define one of these systems, which is then simulated by the computer with a human subject as the other system.

The problems in writing such a program stem from the lack of an adequate and precise psychological theory of human learning and from the complexity and uniqueness of the verbal repertoire with which a subject enters the situation.

A program is presented which establishes a behavior pattern in the subject by using only stimuli which are meaningless to him at the beginning of the interaction; he might e.g. label any stimulus or any response “right” or “wrong” if he felt like doing so. The responses were given by means of 16 on‐off switches, the stimuli consisted of light patterns in 27 lamps. The patterns were contingent on the foregoing stimulus response sequence and they were generated by the computer. The meaning of the program (unknown to the subject) was to teach operations of binary arithmetic. The only instruction given was that the program simulated a first contact by radio with inhabitants of another planet.

The introspection protocols revealed that the subjects could remain ignorant of the real purpose of the program and attach quite a different meaning to their interaction with the computer, even in cases where the intended behavior‐pattern was successfully taught.

In conclusion the method of studying human behavior by modifying the program governing the computer which interacts with the subject is discussed in relation to a more static and statistical approach.
The geometry of log‐normal and related distributions and an application to tracer‐dilution curves
Authors: Wise M. E.
Published: April 2008

Summary

Most of a typical log‐normal curve lies very close to two straight lines, namely the tangents at its points of inflection. This holds good for nearly all the rising part of the curve and for most of the top half beyond the maximum.

When loge (t – to) is normally distributed with standard deviation s̀, whether the whole curve can be observed or not, s̀, to, the mean, the mode and the area under the whole curve can be derived from the triangle formed by these two tangents and the base line. The triangle also provides a simple test of goodness‐of‐fit. The corresponding inflection triangles of two other skew distributions are investigated in outline namely a chi2 (or gamma) distribution and one arising in Brownian movement or random walk in one dimension with drift. These are compared with the log‐normal one. The normal distribution and its inflection triangle are given as a limiting case of the log‐normal one and it is shown that the curve on the cover of Statistica Neerlandica cannot be a normal one.

The application is to the extrapolation problem in heart dye‐dilution curves, which record the distribution of passage times of an indicator through the lungs and heart. The usual semi‐log extrapolation for determining the area under the complete curve is discussed critically; it is shown how the inflection triangle provides a simpler procedure that is probably more accurate. The general formulae, an outline of the application and numerical tables for 0 < s̀ 0.8 are given in the main text; the mathematical derivations of all the basic formulae are in an appendix (sections 11 to 16).

The information needed for practical applications without studying the theory is contained in sections 3 to 6 and the associated tables and figures.
Stochastic Programming
Authors: Wessels J.
Published: April 2008

This report presents an approach to stochastic programming. It treats mainly the difficulties arising in formulating the problem and the possibilities to derive a deterministic problem by which it can be replaced. In a sense the approach of this report unifies different viewpoints on stochastic programming problems as they have been published in the literature.
On Some Nonparametric Tests of Dispersion
Authors: Peritz Eric
Published: April 2008

Let X and Y be random variables with distribution functions F and G and medians ζand η, respectively. X will be said to be more dispersed about the median than Y if F(x+ζ) – F(–x+ζ) G (x+η) – G (–x+η)for all x > O, with sharp inequality holding for some positive x. Asymptotically nonparametric tests for the hypothesis that F (x+ζ) = G (x+η) against alternatives of the above type (for ζ and η unknown), provided F(x+ζ) (but not necessarily G (x+η)) is symmetric and Fand G have bounded densities, are constructed from a subclass Of SUKHATME'S modified generalized U ‐ statistics [12]. One simple test of this subclass turns out to be the MANN‐WHITNEY test as performed on the |Xi–ζ| and | Yj–η| where ζ and η are the corresponding sample medians. Consistency and PITMAN efficiencies of some of the tests proposed are discussed under two families of alternatives in which the Y's differ from the X's through departure from symmetry as well as by being more (less) dispersed: a model of “heterogeneous response” and the wellknown gross error model. The usual scale alternatives are also studied and the relationship of our tests to those previously given in the literature is pointed out.