Judul: Logistic Regression Model Studies on Case-Control Data with Three-Stage Sampling
Abstrak: If the sample is taken by using multistage random sampling, through reducing sample size in the next stage, then the ordinary logistic models can’t be used. This data will be analyzed using logistic models with the additional intercept. This research studied the application of addition intercept terms in logistic regression for case control study used multi stage random sampling. Furthermore, this research compared between the model which was formed and the model of the frame sampling data. The addition intercept in logistic models was able to describe the pattern of relationship explanatory variable with response variable. Missing information decreases with increasing number of samples that observed. Average of missing information in the third stage tends to be smaller than in the second stage, because the third stage has more homogeneous sample units than the second stage. The average of missing information is smaller than the average reduction in the number of samples when using multi-stage random sampling, so this sampling technique is also suitable for use in research aimed at predicting the probability of case. Moreover the use of the sampling technique can reduce the sampling cost.
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Judul: Parameter Estimation Of Correlated Outcome And Covariates Measured With Error In Logistic Regression
Abstrak: In epidemiological studies, it is common to have binary data as the response variable. Hence, the common model applied to represent the relationship between the binary outcome and risk factors is logistic regression. Problems that commonly occur in binary data are intra-class correlation in the outcome variable and measurement error or misclassification in the covariates/risk factors. An alternative statistical procedures, William's procedure and Generalized Estimating Equation for correlated outcome and direct adjustment for measurement error, are used to handle these problems. The application of these methods is implemented to the Children Nutrient Status Data. The data is obtained from the study conducted in June 2000 - October 2000, involving 402 children under five years old in three locations in Central Java. In the analysis of intra-enumerator data, there is an indication of the presence of intra-correlation between data co llected and enumerator.
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Judul: Nanokristalin Pirit (FeS2) sebagai Material Semikonduktor Fotovoltaik.
Abstrak: Teknologi fotovoltaik adalah suatu proses yang dapat mengubah sinar matahari menjadi energi listrik dengan media semikonduktor. Penggunaan sel surya untuk fotovoltaik hanya dapat mengonversi radiasi matahari menjadi energi listrik kurang dari 20%. Efisiensi akan meningkat ketika material semikonduktor untuk fotovoltaik dibuat menjadi ukuran nano. Pirit merupakan salah satu material semikonduktor fotovoltaik yang memiliki energi pita celah (Eg) dalam kisaran 0.8–0.95 eV. Energi pita celah tersebut terbukti meningkat ketika disintesis dengan metode hidrotermal menggunakan beragam molar [S]:[Fe] pada suhu 200 °C dalam 24 jam. Nilai energi pita celah yang dihasilkan adalah 1.58–2.073 eV. Ukuran nanokristalin pirit yang dihasilkan berada pada kisaran 21.04–58.77 nm menurut data Particle Size Analyzer. Besarnya ukuran nanokristal pirit yang tumbuh kurang dari 50 nm merupakan poin penting untuk aplikasi fotovoltaik.
Keyword: Hidrotermal, fotovoltaik, nanokristal, pirit