Part I.
A national department store wants to know the proportion of customers that leave the store with a purchase. A random sample of 75 customers is taken and 51 leave the store with a purchase.
1. Construct a 90% confidence interval for the proportion of customers that leave with a purchase.
2. What is the margin of error at 90% confidence?
3. Construct a 90% confidence interval for the proportion of customers who leave with a purchase for a random sample of 120 customers. How does the size of this interval change from the interval in #1 above?
4. How large of a sample is required to be taken for the error of the estimate (margin of error) to be within + .04 of the population proportion?