Judul: Data Hilang Dalam Analisis Pohon Regresi (Studi Kasus: Tingkat Keberhasilan Mahasiswa Pascasarjana IPB)
Abstrak: The objective of this research are to build regression tree which is contains of missing value to estimate efficacy level of Bogor Agricultural University’s post graduate students and to study about factors that influence efficacy level of Bogor Agricultural University’s post graduate students for each major. Missing value in Classification and Regression Trees (CART) could be handled by nonparametric approach based on iteration of regression tree classification. Each major contains of missing value in their predictor variable. Therefore, surrogates variable is been used to impute this missing value. This variable has high association with primer variable that contains of missing value that will be use as surrogate variable. Efficacy level that researcher want to see is Bogor Agricultural University’s post graduate students academic abilities. This point can be count by post graduate GPA and period of post graduate study. Therefore, factors which are influence efficacy level of Bogor Agricultural University’s post graduate students will be done by regression tree approaching. This research shows that missing value in large amount of value causes increasing of error level in regression tree classification and decreasing of prediction accuracy. This shows that missing value still become a serious problem in CART. The variable that has high association with primer variable that contains missing value will be use as surrogate variable. Regression tree that built from missing value with surrogates will give the best result if we compare it with regression tree that built without surrogates. As a result, post graduate degree in Bogor Agricultural University need to consider age, gender, accreditation, bachelor degree’s Grade Prediction Academic (GPA), profession, and duration from bachelor to post graduate degree variables, because this factors influence students efficacy level in each 16 majors for a period of study. While to produce higher post graduate’s GPA, they need to concern about duration period from bachelor to post graduate degree, earlier college status, acceptance status, age, and accreditation variables. Bogor Agricultural University’s post graduate need to consider all variables that mentioned to produce quality students in future.
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Judul: Pohon Klasifikasi dan Pohon Regresi Keberhasilan Mahasiswa Pascasarjana Program Studi Statistika IPB
Abstrak: Selama tiga tahun terakhir, terlihat sejumlah mahasiswa Sekolah Pascasarjana Departemen Statistika tidak mampu memenuhi persyaratan akademik yang dibebankan kepada mahasiswa selama dua semester pertama. Oleh karena itu, penting untuk memahami faktor-faktor yang mempengaruhi prestasi siswa dengan melacak latar belakang pendidikan sarjana mereka dalam hubungannya dengan prestasi akademik mereka. Faktor-faktor tersebut dapat ditentukan dengan menggunakan teknik pohon regresi. Hasil penelitian menunjukkan bahwa statistik pekerjaan, status universitas dan GP A menentukan prestasi mahasiswa di Program Studi Statistika. Mahasiswa dari universitas BHMN menunjukkan kemampuan yang lebih unggul jika dibandingkan dengan mahasiswa dari universitas non BHMN Jawa dan luar Jawa
Keyword: metode CART, GP A, statistik deskripsi, pohon klasifikasi, pohon regresi

Judul: Karakterisasi Optik dan Listrik Film LiTaO3 (Lithium Tantalate) pada Substrat Silikon [Si(111)] Tipe-n/n+
Abstrak: Telah berhasil dibuat film LiTaO3 pada substrat silikon [Si(111)] tipe-n/n+ dengan variasi suhu annealing selama 8 jam pada suhu 550 oC, 575 oC, 600 oC, dan 625 oC. Metode yang digunakan yaitu Chemical Solution Deposition (CSD) dengan spin coating berkecepatan putar 3000 rpm selama 30 detik dalam kelarutan 1 M. Analisis energi band gap menggunakan metode Tauc Plot menghasilkan nilai sebesar 2.59 - 2.72 eV. Hasil analisis XRD untuk film LiTaO3 pada suhu annealing 600 oC menunjukkan bahwa struktur kristalnya membentuk hexagonal dengan parameter kisi a = b = 5.199Å dan c = 13.890Å. Hasil uji optik menunjukkan bahwa film LiTaO3 dapat mengabsorbsi spektrum Inframerah dekat dengan transisi indirect. Hasil uji listrik menunjukkan bahwa film LiTaO3 termasuk material semikonduktor
Keyword: LiTaO3, electrical properties, optical properties, n/n+-type silicon [Si(111)], XRD, Karakterisasi XRD, X-Ray difraction, Metode tauc plot, Konduktivitas, Konstantra dielektrik