A company produces a womens bowling ball that is supposed to

A company produces a women\'s bowling ball that is supposed to weigh exactly 14 pounds. Unfortunately, the company has a problem with the variability of the weight. In a sample of 11 of the bowling balls the sample standard deviation was found to be 0.71 pounds. Construct a 95% confidence interval for the variance of the bowling ball weight. Assume normality.

a) What is the lower limit of the 95% interval? Give your answer to three decimal places.  

b) What is the upper limit of the 95% interval? Give your answer to three decimal places.  

c) Which of the following assumptions should be checked before constructing the above confidence interval?

the data need to be right skewedthe data need to follow a normal distribution     the data need to follow a chi-square distributionthe data need to have small variance

Solution

a) lower limit of the 95% interval 13.523,

b) upper limit of the 95% interval  14.477

c)the data need to follow a normal distribution