Part variability is critical in the manufacturing of ball be

Part variability is critical in the manufacturing of ball bearings. Large variances in the sizeof the ball bearings cause bearing failure and rapid wearout. Production standards call fora maximum variance of .0001 when the bearing sizes are measured in inches. Asample of15 bearings shows a sample standard deviation of .014 inches.

a. use a=.10 to determine weather the sample indicates that the maximum acceptable variance is being exceeded.

b. Compute the 90% confidence interval estimate of the variance of the ball bearing in the population

Back of the book answer:

a.)

X^2=27.44

P-val between .01 and .025

Reject null hyp., variance exceeds maximum requirements

b.)

.00012 to .00042

Obviously I know the final answer, but what are the steps to get there

Solution