Thompson Machine Works purchased several new, highly sophisticated machines. The production department needed some guidance with respect to qualifications needed by an operator. Four variables were listed.

X1 = Length of time employee was a machinist

X2 = Mechanical aptitude test score

X3 = Prior on -the-job rating

X4 = Age

Performance on the machine is designated Y

The following are the results of the regression analysis;

Independent

Variables Coefficient t-stat

Intercept 11.600 2.95

X1 0.400 1.23

X2 0.286 3.71

X3 0.112 4.10

X4 0.002 1.86

a. Write out the multiple regression equation.

b. How many independent variables are there?

c. Assuming the sample size was very large (the degrees of freedom is equal to 100), would you consider eliminating any of the independent variables?