代做STA 137作业、代做JobProaciency留学生作业、代写Python实验作业、代写c++/python课程设计作业
Monday, January 7 Times series examples (Handout 1).Wednesday, January 9 Review of regression (Handout 2).Friday, January 11 Review of regression (Handouts 2 and 3).Homework 1: Due on Friday, January 18You may form a group of 3 students registered in this course and submitone completed homework for the group. The front page should display onlythe names of the students in the group. The actual work should start from thesecond pageYou will and a data set (JobProaciency) on the job prociency of 25 applicantsfor entry level clerical positions in a government agency. The scoreson four tests (X1; X2; X3; X4) and the job proaciency scores (Y ) for the 25 applicantsare given in the data set. A multiple regression is to be ?tted to thisdataYi = 0 + 1Xi1 + 2Xi2 + 3Xi3 + i4Xi4 + "i; i = 1; : : : ; n = 25;where f"ig are independent N(0; 2) variables.1. (a) Obtain a histogram for each of the variables. Are there noteworthyfeatures in the plots? Comment.(b) Obtain a matrix plot of the data (ie, plot all the variables against each other(R command: pairs)). Also obtain the correlation matrix. What do the plotssuggest about the nature of relationship between Y and each of the predictorvariables? Discuss. Does it seem that there is a problem of multicollinearity?Explain.(c) Fit a multiple regression model to the data. Obtain the parameter estimates,their standard errors, analysis of variance table, R2 and R2adj .(d) Does it seem that all the independent variables need to be retained in theregression model? If you consider deleting only one independent variable, whichis the best candidate for deletion? Explain your answers.2. The questions here are on the atted model in (1c).(a) Obtain a plot of the observed against the atted Y values. Also plot theresiduals against the atted values. Does it seem that the ?tted model is reasonable?Do you suspect any nonlinearity? Is the assumption of equal variance ofthe errors (ie, "iís) reasonable here? Explain your answers.1(c) Obtain a histogram of the residuals. Also obtain a normal probability plot ofthe residuals, and the correlation between the residuals and the normal scores.Is the assumption of normality of the errors reasonable? Explain.3. (a) This question is on model selection by backward elimination. Startingwith the full model, delete one variable at a time. At each step, drop thevariable that is the best candidate for deletion. In this way, you will have 5models: the largest one with all 4 independent variables, and the smallest onehas none. For each model, and the AIC and BIC values. Find the best model(s)selected by the AIC and BIC criteria. Fit these anal selected model(s), obtainthe parameter estimates, their standard errors, R2 and R2adj .(b) Use the AIC and the BIC criteria to select the best among all possible regressionmodels. Fit these anal selected model(s), obtain the parameter estimates,their standard errors, R2 and R2adj .因为专业,所以值得信赖。如有需要,请加QQ:99515681 或邮箱:
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