The manager of a restaurant in a large city claims that waiters working in all restaurants in his city earn an average of $150 or more in tips per week. A random sample of 25 waiters selected from restaurants of this city yielded a mean of $139 in tips per week with a standard deviation of $28. Assume that the weekly tips for all waiters in this city have a normal distribution.

a. Using the 1% significance level, can you conclude that the manager's claim is true? Use

both approaches.

b. What is the Type I error in this exercise? Explain. What is the probability of making such

an error?