Question: In a manufacturing process the assembly line speed (feet per minute) was thought to affect the number of defective parts found during the inspection process. To test this theory, managers devised a situation in which the same batch of parts was inspected visually at a variety of line speeds. They collected the following data:

Line speed(ft/min)                 Number of Defective Parts Found

        20                                                  21

        20                                                  19

        40                                                  15

        30                                                  16

        60                                                  14

        40                                                  17

a. Develop a scatter chart with line speed as the independent variable. What does the scatter chart indicate about the relationship between line speed and the number of defective parts found?

b. Use the data to develop an estimated regression equation that could be used to predict the number of defective parts found, given the line speed. What is the estimated regression model?

c. Test whether each of the regression parameters b0 and b1 is equal to zero at a 0.01 level of significance. What are the correct interpretations of the estimated regression parameters? Are these interpretations reasonable?

d. How much of the variation in the number of defective parts found for the sample data does the model you estimated in part b explain?