The labor estimation group at Sturdy Electronics, a contract electronics manufacturer of printed circuit boards, wants to simplify the process it uses to quote production costs to potential customers. They have identified the primary drivers for production time (and thus production cost) as being the number of electronic parts that can be machine installed and the number of parts that must be manually installed. Accordingly, they wish to develop a multiple regression model to predict production time, measured as minutes per board, using a random sample of 25 recent product quotations. A portion of the data is shown in the accompanying table.

Production Time Machine Parts Manual Parts

9.1.............................275.........................14

10.8...........................446.........................12

⋮...................................⋮...........................⋮

15.5...........................618.........................16

a. What is the sample regression equation?

b. Predict production time for a circuit board with 475 machine-installed components and 16 manually-installed components.

c. What proportion of the sample variability in production time is explained by the two explanatory variables?

d. At the 5% significance level, are the explanatory variables jointly significant? Are they individually significant?