Exam 15: Multiple Regression Model Building

SCENARIO 15-6 Given below are results from the regression analysis on 40 observations where the dependent variable is the number of weeks a worker is unemployed due to a layoff (Y)and the independent variables are the age of the worker ( ), the number of years of education received ( ), the number of years at the previous job ( ), a dummy variable for marital status ( 1 = married, 0 = otherwise), a dummy variable for head of household ( 1 = yes, 0 = no)and a dummy variable for management position ( 1 = yes, 0 = no). The coefficient of multiple determination ( )for the regression model using each of the 6 variables as the dependent variable and all other X variables as independent variables are, respectively, 0.2628, 0.1240, 0.2404, 0.3510, 0.3342 and 0.0993. The partial results from best-subset regression are given below: -Referring to Scenario 15-6, what is the value of the Mallow's statistic for the model that includes and ?

A regression diagnostic tool used to study the possible effects of collinearity is

SCENARIO 15-3 A chemist employed by a pharmaceutical firm has developed a muscle relaxant.She took a sample of 14 people suffering from extreme muscle constriction.She gave each a vial containing a dose (X)of the drug and recorded the time to relief (Y)measured in seconds for each.She fit a curvilinear model to this data.The results obtained by Microsoft Excel follow SUMMARY OUTPUT -Referring to Scenario 15-3, suppose the chemist decides to use an F test to determine if there is a significant curvilinear relationship between time and dose.The p-value of the test is ________.

Collinearity will result in excessively low standard errors of the parameter estimates reported in the regression output.

In stepwise regression, an independent variable is not allowed to be removed from the model once it has entered into the model.

SCENARIO 15-2 In Hawaii, condemnation proceedings are under way to enable private citizens to own the property that their homes are built on.Until recently, only estates were permitted to own land, and homeowners leased the land from the estate.In order to comply with the new law, a large Hawaiian estate wants to use regression analysis to estimate the fair market value of the land. The following model was fit to data collected for n = 20 properties, 10 of which are located near a cove. Model 1: where Y Sale price of property in thousands of dollars Size of property in thousands of square feet 1 if property located near cove, 0 if not Using the data collected for the 20 properties, the following partial output obtained from Microsoft Excel is shown: SUMMARY OUTPUT -Referring to Scenario 15-2, given a quadratic relationship between sale price (Y)and property size , what null hypothesis would you test to determine whether the curves differ from cove and non-cove properties?

In multiple regression, the __________ procedure permits variables to enter and leave the model at different stages of its development.

SCENARIO 15-6 Given below are results from the regression analysis on 40 observations where the dependent variable is the number of weeks a worker is unemployed due to a layoff (Y)and the independent variables are the age of the worker ( ), the number of years of education received ( ), the number of years at the previous job ( ), a dummy variable for marital status ( 1 = married, 0 = otherwise), a dummy variable for head of household ( 1 = yes, 0 = no)and a dummy variable for management position ( 1 = yes, 0 = no). The coefficient of multiple determination ( )for the regression model using each of the 6 variables as the dependent variable and all other X variables as independent variables are, respectively, 0.2628, 0.1240, 0.2404, 0.3510, 0.3342 and 0.0993. The partial results from best-subset regression are given below: -Referring to Scenario 15-6, the variable should be dropped to remove collinearity?

The Variance Inflationary Factor (VIF)measures the correlation of the X variables with the Y variable.

Collinearity is present if the dependent variable is linearly related to one of the explanatory variables.

The stepwise regression approach takes into consideration all possible models.

SCENARIO 15-4 The superintendent of a school district wanted to predict the percentage of students passing a sixth-grade proficiency test.She obtained the data on percentage of students passing the proficiency test (% Passing), daily mean of the percentage of students attending class (% Attendance), mean teacher salary in dollars (Salaries), and instructional spending per pupil in dollars (Spending)of 47 schools in the state. Let Y = % Passing as the dependent variable, Attendance, Salaries and Spending. The coefficient of multiple determination ( )of each of the 3 predictors with all the other remaining predictors are, respectively, 0.0338, 0.4669, and 0.4743. The output from the best-subset regressions is given below: Following is the residual plot for % Attendance: Following is the output of several multiple regression models: -Referring to Scenario 15-4, there is reason to suspect collinearity between some pairs of predictors.

A microeconomist wants to determine how corporate sales are influenced by capital and wage spending by companies.She proceeds to randomly select 26 large corporations and record information in millions of dollars.A statistical analyst discovers that capital spending by corporations has a significant inverse relationship with wage spending.What should the microeconomist who developed this multiple regression model be particularly concerned with?

The _______ (larger/smaller)the value of the Variance Inflationary Factor, the higher is the collinearity of the X variables.

SCENARIO 15-6 Given below are results from the regression analysis on 40 observations where the dependent variable is the number of weeks a worker is unemployed due to a layoff (Y)and the independent variables are the age of the worker ( ), the number of years of education received ( ), the number of years at the previous job ( ), a dummy variable for marital status ( 1 = married, 0 = otherwise), a dummy variable for head of household ( 1 = yes, 0 = no)and a dummy variable for management position ( 1 = yes, 0 = no). The coefficient of multiple determination ( )for the regression model using each of the 6 variables as the dependent variable and all other X variables as independent variables are, respectively, 0.2628, 0.1240, 0.2404, 0.3510, 0.3342 and 0.0993. The partial results from best-subset regression are given below: -Referring to Scenario 15-6, what is the value of the Mallow's statistic for the model that includes ?

SCENARIO 15-6 Given below are results from the regression analysis on 40 observations where the dependent variable is the number of weeks a worker is unemployed due to a layoff (Y)and the independent variables are the age of the worker ( ), the number of years of education received ( ), the number of years at the previous job ( ), a dummy variable for marital status ( 1 = married, 0 = otherwise), a dummy variable for head of household ( 1 = yes, 0 = no)and a dummy variable for management position ( 1 = yes, 0 = no). The coefficient of multiple determination ( )for the regression model using each of the 6 variables as the dependent variable and all other X variables as independent variables are, respectively, 0.2628, 0.1240, 0.2404, 0.3510, 0.3342 and 0.0993. The partial results from best-subset regression are given below: -Referring to Scenario 15-6, what is the value of the variance inflationary factor of Manager?

SCENARIO 15-6 Given below are results from the regression analysis on 40 observations where the dependent variable is the number of weeks a worker is unemployed due to a layoff (Y)and the independent variables are the age of the worker ( ), the number of years of education received ( ), the number of years at the previous job ( ), a dummy variable for marital status ( 1 = married, 0 = otherwise), a dummy variable for head of household ( 1 = yes, 0 = no)and a dummy variable for management position ( 1 = yes, 0 = no). The coefficient of multiple determination ( )for the regression model using each of the 6 variables as the dependent variable and all other X variables as independent variables are, respectively, 0.2628, 0.1240, 0.2404, 0.3510, 0.3342 and 0.0993. The partial results from best-subset regression are given below: -Referring to Scenario 15-6, the variable X6 should be dropped to remove collinearity?

SCENARIO 15-6 Given below are results from the regression analysis on 40 observations where the dependent variable is the number of weeks a worker is unemployed due to a layoff (Y)and the independent variables are the age of the worker ( ), the number of years of education received ( ), the number of years at the previous job ( ), a dummy variable for marital status ( 1 = married, 0 = otherwise), a dummy variable for head of household ( 1 = yes, 0 = no)and a dummy variable for management position ( 1 = yes, 0 = no). The coefficient of multiple determination ( )for the regression model using each of the 6 variables as the dependent variable and all other X variables as independent variables are, respectively, 0.2628, 0.1240, 0.2404, 0.3510, 0.3342 and 0.0993. The partial results from best-subset regression are given below: -Referring to Scenario 15-6, the model that includes should be among the appropriate models using the Mallow's statistic.

If a group of independent variables are not significant individually but are significant as a group at a specified level of significance, this is most likely due to