A manufacturing process, the assembly line speed (X, measured in feet per minute) was thought to affect the number of defective parts (Y, measured in numbers) found during the inspection process. A simple regression model is assumed to predict Y from X. The following is the computer output from a random sample of 20 trials.
Predictor Coeff StdDev
Constant 217.0 0.5
X -1.5 1.0
8. To test if the simple regression model is significant, which one of the following is the value of the test statistic ?
(a) t = 0.3 (b) t = 2.4 (c) F = 2.25 (d) F = 5.76 (e) none of these
9. To test if the slope of the regression line is less than -0.5 or not, the test statistics is
(a) t = -1 (b) t = 1 (c) F = 1 (d) all of the above (e) none of the above
10. The estimated average number of defectives on 120 feet per minute is closest to
(a) 12 (b) 21 (c) 28 (d) 32 (e) 37
11. The correlation coefficient between X and Y is equal to
(a) -1/3 (b) 1/3 (c) 2/3 (d) 1/9 (e) none of these