Allante Pizza delivers pizzas throughout its local market area at no charge to the customer. However, customers often tip the driver. The owner is interested in estimating the mean tip income per delivery. To do this, she has selected a simple random sample of 12 deliveries and has recorded the tips that were received by the drivers. These data are

a. Based on these sample data, what is the best point estimate to use as an estimate of the true mean tip per delivery?
b. Suppose the owner is interested in developing a 90% confidence interval estimate. Given the fact that the population standard deviation is unknown, what distribution will be used to obtain the critical value?
c. Referring to part b, what assumption is required to use the specified distribution to obtain the critical value? Develop a box and whisker plot to illustrate whether this assumption seems to be reasonably satisfied.
d. Referring to parts b and c, construct and interpret the 90% confidence interval estimate for the population mean.