Judul: The Problem Of Overdispersion In Logistic Regression
Abstrak: Overdispersion is caused by the variability of the response probability or correlatioti between the bitiary responses. The aim of this research is coniparing the parameter estiliiate from Logistic Regression (LR), Willialiis Method (WM), atid Beta-Binomial Regression (BBR). From tlie value of tlie pearson chi-square and deviance, the logistic regression of acadeliiic achievement exhibit overdispersion. The parameter estimate of LR, WM, and BBR are not significant different visually. The difference is seen obviously from tlie value of standard error. The value of standard error from WM and BBR are greater than LR. It's as a conseqoently of overdispersion. In other word, tlie standard error from LR doesn't accolllrnodate tlie problem, causing the valrte of standard error from LR is underestimate. Based on tlie result of analyse, tlie GPA TPB call be seen as an indicator ofacade~nica cliievement in the next level. Based on tlie result of simulation, it is tested parameter estitnate and standard error from some cases of correlation between the binary responses (overdispersion) for the three methods. As a result, When there is no overdispersion, tlie parameter estimate and the stantlard error from the three methods are not significant different. When tliere is overdispersion, the parameter estimate from LR, WM, and BBR are not signilica~itl ii%crcnt, but thc valuc oI"stantli~~-c(1rr or from WM ;~ndB BR arc grcatcr tlia~iL R. Tlie valuc of standard error fiom LR is relitlively similar ibr all of the cases, while the value ofstandard error from WM and BBR increase as the correlation raises.
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Judul: Kajian Pengaruh Overdispersi Dalam Regresi Poisson
Abstrak: Data jumlah (count data) yang diasumsikan menyebar Poisson dapat dianalisis dengan regresi Poisson. Terkadang dalam suatu penelitian seriDg ditemukan permasalahan keragaman data yang Icbih hesar dari nilai tengahnya. hal ini mcrupakan penyimpangan dari asumsi sebaran Poisson. Fenomena ini discbut deoa;1n overdispcrsi. Jika data jumlah yang teroverdispersi dianalisis dengan regresi Poisson maka galat baku penduga koefisien regresi akan lebih keeil dari nilai sebenamya (underestjmate). Hal ini akan mengakibatkan uji keberartian peubah bebasnya menjadi tidak benar. Pendekatan Idasik yang sering digunakan untuk mengatasi, data jumlah yang teroverdispersi adalah regresi binomial negatif. Kajian pengaruh overdispersi dalam regresi 1!oissori';.kaJi ini ,menunjukkan bahwa data yang mengandung overdispersi tidak dapat dianalisis ~gan regre"$i poisson. K.arena ga1at baku penduga koefisien regresi yang dihasilkan nilainya lebih keeU dari nHai sebenamya (underestimate). Tampilan data dengan nilai kesalahan mutlak (absolute error)dapat meriunjukkan bal itu. Regresi binomial negatif secara teori mengandung parameter dispersi. Besamya overdispersi dapat diduga dengan regresi binomial negatif dan hasil dugaan tersebut juga digunakan dalam mCLlduga galat baku peubah bebasnya. Oleh karena itu, plat baku ylUlg diperoleh merupakan galat baku yang mendekati nilai sebenamya. Kajian ini menunjukkan hal itu, yakni galat baku penduga koefisien regresi mendekati nilai sebenamya Dengau demikian pengujian
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Judul: Elektrodeposisi Film Tipis Semikonduktor Cu2ZnSnS4 (CZTS) pada Substrat Kaca ITO
Abstrak: Semiconductor Cu2ZnSnS4 (CZTS) thin film that can be used as absorber layers on solar cell module was made via electrodeposition method. CZTS thin film was electrodeposited on the surface of a silicate glass coated with a thin layer of indium tin oxide (ITO). Deposition process was done using potentiostatic mode at room temperature with a potential of 1.05 V for 30, 45, and 60 minutes, followed with annealing the film at 2 different temperatures, 500 ºC using furnace and 180 ºC using hot plate, both treatments for 45 minutes in N2/H2S atmosphere. The X-ray difractograms were analyzed using Match 2 program and showed that the CZTS thin films had kesterit crystalline structure, with a low percentage of CZTS phase. The thin film also contained secondary phases such as Cu2S, ZnS, and SnS. The obtained CZTS thin films had a thickness between 1.039 and 1.676 μm. Absorption study showed that the band gap energy of CZTS thin films which was annealed using furnace ranged from 1.50 to 1.52 eV, whereas that annealed using the hot plate was not observed. The band gap energy value showed that CZTS thin films can be used as sunlight absorber layers on solar cell. The formation of CZTS crystal film on this investigation was effectively performed using furnace annealing process at a temperature of 500 ºC with deposition time of 45 minutes.
Keyword: Thin film, Electrodeposition, Cu2ZnSnS4