Judul: Perbandingan Tingkat Kepentingan Peubah dalam Regresi Linear Berganda antara Model Konvensional dan Metode Pratt, Sigit D.S., Rahmatullah
Abstrak: The objective of this research is to compare various methods in determining variable importance in multiple linear regression. In multiple linear regression analysis, it is of interest to rank order and scale predictors in terms of their importance to dependent variable. In one conventional method, variables are ranked based on their standardized coefficients obtained from regression model, which is regarded as their relative importance. In other method, partial correlation between the predictors and dependent variable is used as a measure of variable importance. Pratt in 1987 proposed different method to determine variable importance within several assumptions that the variables have to met. Specifically, this method gives an estimation to the importance measure. This research reviews three methods, namely the standardized coefficient, partial correlation, and Pratt method. Two sets of data with specific variable importance parameters were generated. One set was generated under multicollinearity condition, while the other was without it. Three kind of regression models were constructed from the data with each contained two, five and eight variables, respectively. Each model was then simulated in 50 turns, in each of which importance measures were obtained using the three methods. The measures' averages were then compared to the importance parameters to determine their performance. The result shows that under no multicollinearity condition Pratt method gives better estimate to variable importance parameter in regression model with 5 and 8 variables, compared to conventional methods. Meanwhile, under multicollinearity condition the three methods performance are about the same. Pratt method also consistently produces smaller variance than the other two, indicating that this method is more stable in measuring the variable importance.
Keyword: Pratt method, multicollinearity data generation, simulation, multiple linear regression.

Judul: Kajian metode pendugaan pada model regresi dengan peubah penjelas bersifat acak
Abstrak: Regression analysis is a statistical method to evaluate the relationship between a variable with other variables. Model I regression analysis describes the one-way relationship between variable X and variable Y with the value of X as fixed variable or measured without error. Model I regression analysis uses Ordinary Least Square (OLS) as an estimation method. Model II regression analysis is a regression model with predictors variable that becomes a random variable. There are two estimation methods of model II regression analysis, ordinary least product regression (Model IIA) and major axis regression (Model IIB). The convenience of using model I regression analysis with OLS estimation method causes many researchers to use this model as a model regression analysis with random predictor variables. The purpose of this study is to compare model I regression analysis (OLS estimation method) and model II regression analysis (ordinary least product estimation method and major axis regression estimation method). The data used in this research are simulation data where response variable (Y) and predictor variable (X) are random. The result of this study showed for predictor variable is random, ordinary least product regression is the best estimation method compared to the other methods because it produces the smallest value of bias and the smallest value of mean square error. In this condition, OLS can be used for the estimate parameter of simple linier regression model if the correlation value between predictor variable (X) and response variable (Y) is high (r ≥ 0.9).
Keyword: Bogor Agricultural University (IPB), Model IIB, Model IIA, Model I, mean square error, correlation

Judul: Embriogenesis ikan buta (Astyanax fasciatus)
Abstrak: Ikan buta Astyanax fasciatus adalah spesies ikan unik dari famili Characidae yang menempati perairan dalam gua di Wilayah La Cueva Chica-San Luis Potasi-Mexico. Ikan ini memiliki mata yang tereduksi (Blind Cavefish) dan warna kulit merah muda, pucat serta mengkilap.
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