You're attempting to prove that the variance of the dollar value of products bought on line for a certain target market is greater than $100. To test this you choose a random sample of 20 customers and find out that the variance of this sample is $150.
a) Set up hypotheses and test to find out whether or not the population variance is larger than $100.
b) Based on your sample variance, develop a 95% confidence interval, which will contain true variance 95% of the time. This is, of course, by definition of confidence interval.