Judul: Identifikasi Peubah-Peubah yang Mempengaruhi Kualitas Produk Batang Kawat Baja Cold Heading
Abstrak: Cold heading steel wire rod is one of the steel products manufactured by WRM division at PT Krakatau Steel (Persero) Tbk. The flow of steel wire rod manufacturing process at the division WRM consists of two line are distinguished by the cooling technology used. Steel wire rod steel mechanical properties, among others, yield strength/YS, tensile strength/TS, and elongation/EL. The diversity of the mechanical properties of the steel value is thought to be influenced by several variables such as variable line difference (engine), variable inputs (raw materials/ chemical composition), and the production process variables (temperature rolling process). Based on the results of the test vector median value of the difference in the second line was found that there was no difference in the line affect the mechanical properties of steel produced, while the results of different time periods stated production are wide differences in the time period of production or the data is not homogeneous. Furthermore, based on the results of exploratory evaluation of production performance by looking at the specification limit and the linkage between variables chart showing the movement of the diversity generated in the production of different time periods. The variable chemical composition Si, temperature LHD and SMC suspected to have considerable influence on the mechanical properties of steel change variables, especially variables TS.
Keyword: the movement graph, specification limits

Judul: Penerapan Regresi Peubah Ganda pada Sifat-Sifat Mekanik Baja Batang Kawat Karbon Tinggi.
Abstrak: Baja batang kawat karbon tinggi grade KS1062A berdiameter 5 mm merupakan salah satu produk baja yang diproduksi oleh pabrik Wire Rod Mill (WRM) di PT Krakatau Steel. Pada proses pembutan baja batang kawat, pabrik WRM memiliki dua line yang dibedakan berdasarkan teknologi pendinginan yang digunakan. Baja memiliki sifat-sifat mekanik yaitu Tensile Strength (TS) dalam kg/mm2, Yield Strength (YS) dalam kg/mm2, dan Elongation (EL) dalam persen. Keragaman nilai sifat-sifat mekanik diduga dipengaruhi oleh kandungan komposisi kimia, perubahan suhu, dan perbedaan line. Pemodelan peubah ganda diperlukan pada data yang memiliki peubah respon lebih dari satu yang tidak saling bebas. Uji signifikansi parameter yang digunakan yaitu statistik Wilks’ Lambda. Berdasarkan hasil uji tersebut, unsur kimia yang berpengaruh nyata secara simultan terhadap ketiga sifat mekanik adalah unsur C, Mn, Si, dan V, sedangkan perubahan suhu dan perbedaan line tidak berpengaruh nyata terhadap sifat-sifat mekanik tersebut. Selain itu, besarnya nilai sifat-sifat mekanik baja juga dipengaruhi oleh perbedaan tanggal produksi.
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Judul: Approximation of the Median of Poisson Distribution Using the Relation of Poisson-Gamma Distribution
Abstrak: A major drawback of median is that median cannot usually be defined in closed form, even in the cases where their distribution functions are known. This study gives an approximation of the closed form for the median of the Poisson distribution by using the relation of Poisson-Gamma distribution. The approximation uses elementary techniques based on the monotonicity of certain sequences involving tail probabilities of the Poisson distribution and the Central Limit Theorem. Furthermore, a closed form expression for the mean absolute deviation 􀜧|􀜰􀰒 􀵆 􀜯􀝁􀝀􁈺􀜰􀰒􁈻| is also studied. The median is relevant because of the fact that it minimizes the mean absolute deviation of a Poisson random variable (􀜰􀰒􁈻 by considering median as central tendency.
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