A server at a local restaurant believes the average tip given by customers is under $20.

To test the claim, the servers during a shift keep track of their tips to collect a sample of 424 customers.

The sample mean is $18.49 with a sample standard deviation of $15.06.

a) What is the Null Hypothesis and the Alternative Hypothesis for the server's claim?

b)Assuming the population is normal, should we use the Normal z-test or the Student's t-test?

c) If we use a 0.05 significance level, what is the critical value for the test?

d) Calculate the value of the test statistic.

e)What is your decision about the null hypothesis and your conclusion about server's claim?