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 12 of the bowling balls the sample standard deviation was found to be 0.65 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 follow a normal distribution
-the data need to follow a chi-square distribution
-the data need to be right skewed
-the data need to have small variance