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: Applying Hidden Logit Model with Randomized Response (Case Study
Abstrak: In 1965 Stanley Warner (Fox & Tracy, 1986) pioneered the randomized response technique to reduce bias response caused by respondents who lied, or did not answer the question given by the interviewer to estimate the sensitive characteristics. Warner model directing respondents to answer either of two sensitive opposite questions. Warner model still has weaknesses, then Simmons (Fox & Tracy, 1986) develops a randomized response technique of Warner model by replacing one question with a question that not associated with the sensitive issues at all (unrelated question model). According to Stem & Steinhorst (Fox & Tracy, 1986) unrelated question model still has weaknesses too and then developed into a forced response model. Maddala (1983) pioneered the development of sensitive attributes in the randomized response technique as a binary response variable associated with several explanatory variables. This development adopts logistic regression to estimate its parameters. Since π* is the population proportion that have sensitive attributes that can not be predicted directly, but estimated by π, Corstange (2004) named this prediction method with hidden logit estimation. This research aimed to find factors that affect a student accessing porn sites. This research obtain that proportion estimator of the population that accessing porn sites is 24%. Variables that significantly influence a student to access pornographic websites such as gender, maternal education, ownership of the laptop and how to connect to the internet. This research also needs to be developed again primarily related to response variables that have more than two categories (multinomial) such as issues about the type of drugs consumed, how many times had an abortion in a population of prostitutes and so on.
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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