The model y = β0 + β1x1 + β2x2 + ε is fit to the data of Exercise 12.21. Selected output i...

The model y = β0 + β1x1 + β2x2 + ε is fit to the data of Exercise 12.21. Selected output is shown here.

Multiple Regression Analysis

a. Write the complete and reduced-form estimated models.

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b. Is the improvement in R2 obtained by adding x3, x4, and x5 statistically significant at α = .05? Approximately what is the p-value for this test?

Exercise 12.21

The manager of documentation for a computer software firm wants to forecast the time required to document moderate-size computer programs. Records are available for 26 programs. The variables are y = number of writer-days needed, x1 = number of subprograms, x2 = average number of lines per subprogram, x3 = x1x2,  and  A portion of the output from a regression analysis of the data is shown here.

Multiple Regression Analysis

a. Write the multiple regression model and locate the residual standard deviation.

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b. Does x3 have a significant, unique predictive value?