Question 1(5 Marks)

The owner of a sporting goods store surveys a group of customers on (i) the average amount spent, and (ii) whether they purchased at least one item of clothing.

The results of a sample of 80 customers are:

Average amount spent:

Standard deviation:

a)Construct a 90% confidence interval for the mean amount spent per shopper.

b)What sample size does he need if he wants to estimate a 95% confidence interval for the mean amount spent to within ?