Judul: The using of CART and CHAID’s method in finding factors that affect students’ achievement of STAKPN Tarutung
Abstrak: Students’ learning achievement is one of indicators that can be used to determine the study quality that conducted by the college. Therefore, to assess the learning quality improvement can be done by investigating the factors that affect students’ achievement. Generally, these factors consist of two parts: internal factors and external factors. Internal factors consist of health, learning interest, learning attitude and religiosity. While external factors consist of campus environment and family environment. The aim of this study is to determine the factors that influence students’ achievement of STAKPN Tarutung by using Classification and Regression Tree (CART) and Chi-square method Automatic Interaction Detection (CHAID). These methods are tree structure methods were used to examine the relationship between the response variable with explanatory variable that influence it. Learning achievement is response variable which is measured by students’ value (GPA). CART method was used when the performance index value used as continuous data, while CHAID method was used when the performance index value used as ordinal data. While the explanatory variables were analyzed consist of 21 variables, such as: origin of school, status of school, majoring, illness, disability, suitability majors, number of siblings, father's education, mother's education, parental income, study schedules, long time to learn, creativity to seek support lecture material, creativity to do assignments, calssroom conditions, facilities and means of lectures, ideological dimensions of religiosity, ritualistic dimension of religiosity, experiential dimension of religiosity, intellectual dimensions of religiosity, and consequential dimension of religiosity. The object of this study is the students of STAKPN (Sekolah Tinggi Agama Kristen Negeri) Tarutung. The source of were got from primary data and secondary data. Primary data was collected by using a questionnaire research instruments. The questionnaire contained a list of questions to determine the identity, educational background, health condition, family situation, campus environment, learning attitude, learning motivation, and the religiosity of the respondent. While secondary data was got from a list of values (GPA) of respondents were obtained from academic section of STAKPN Tarutung. Data collection was conducted in May 2013. The total number of respondents was 176 students. The result of CART analysis showed that variables influence student’s achievement of STAKPN Tarutung row were students’ major in high school, number of students’ siblings, intellectual dimension of religiosity and long time student studying at home. The first variable that splits was high school majors. The respondent was split into 2 groups based on their majoring. Students’ majoring from science consist of 75 respondents and students from social and vocational consist of 101 respondents. Students from science related to the number of siblings. Variable number of siblings split science graduate students group into two groups, namely the number of students who have siblings >3 consist of 59 respondents and students who have a number of relatives ≤3 consist of 16 respondents. Groups of undergraduate students majoring in social studies and related to the intellectual dimension of religiosity. This variable split groups and undergraduate students majoring in social studies into two groups, namely group of students with the intellectual dimension of religiosity categories of never or rarely consist of 25 respondents
Keyword: CART’s method, CHAID’s method, students’ achievement

Judul: Metode CHAID dan korespondensi untuk menentukan faktor-faktor yang berasosiasi dengan keberhasilan studi mahasiswa
Abstrak: The student achievement to pursue a bachelor degree has been influenced by many factors. Previous researches showed that the student’s achievement is associated to NEM score, sex, hometown, motivation, self-confidence, organizational activities, GPA score, family income, parent’s job, environment, and learning methods. This study aimed to determine factors associated to STEI SEBI student achievement. The data was obtained by browsing the academic database for student’s personal records and study history; and by conducting a survey on psychological and external factors in their campus life. A group of 62 STEI SEBI students from 2004 and 2005 years of enrollment is taken as respondents. The CHAID and Correspondence methods are used to determine factors associated to student achievement. The CHAID study finds three significant factors associated to student achievement. They are organizational activities, GPA score, and parent’s job. The correspondence study characterizes successful and failed student profiles. A successful student is profiled as being active in organizational activities, having GPA score at least 2.5, and his/her parent’s job is government or private employee. While a failed student is characterized as non involvement in any organizational activities, GPA score is less than 2.5, and his/her parent’s job is farmer, entrepreneur, or other occupation.
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Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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