Concept explainers
a.
Identify the variable that can be eliminated first to possibly improve the given model.
a.
Answer to Problem 58E
The variable that can be eliminated first to possibly improve the given model is
Explanation of Solution
In order to improve a regression model, the most insignificant independent variable in the model should be eliminated first. The high p-value indicates that the variable is insignificant.
From the multiple regression model, it is clear that the variable
b.
Describe about the
Explain whether the change in
b.
Answer to Problem 58E
The coefficient of determination
Explanation of Solution
The larger value of
Generally, even eliminating an insignificant variable tends to decrease the value of
c.
Obtain the p-value of ANOVA for the original 3-predictor model.
Explain whether the type of change in the p-value for ANOVA represents that removing the variable chosen in Part (a) is a good or bad idea.
c.
Answer to Problem 58E
The p-value of ANOVA for the original 3-predictor model is 0.322.
Explanation of Solution
From the multiple regression output, it is clear that the p-value of ANOVA for the original 3-predictor model is 0.322.
In common, removing an insignificant variable tends to improve the model. Thus, it causes the p-value of ANOVA to decrease.
Thus, if the p-value decreases after removing
d.
Obtain the F-statistic from ANOVA for the given model.
Explain whether there is a change in F-statistic for ANOVA when removing an insignificant variable.
d.
Answer to Problem 58E
The F-statistic of ANOVA for the given model is 1.23.
Explanation of Solution
From the multiple regression output, it is clear that the F-statistic of ANOVA for the given model is 1.23.
In the F-statistic, the numerator is divided by fewer degrees of freedom and the denominator is divided by more degrees of freedom.
The variable that explains little variation than other variables is dropped out as it is an insignificant variable. Hence, if an insignificant variable is dropped out, it causes the F-statistic to increase.
If the F-statistics is increased after removing the insignificant variable, then removing that variable is good idea. Otherwise, it is a bad idea.
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