A scrap metal dealer claims that the mean of its cash sales is ‘no more than $80’, although an Internal Revenue Service agent believes that the dealer is being dishonest. Observing a sample of 20 cash...

A scrap metal dealer claims that the mean of its cash sales is ‘no more than $80’, although an Internal Revenue Service agent believes that the dealer is being dishonest. Observing a sample of 20 cash customers, the agent finds the mean cash sales to be $91, with a standard deviation of $21. Assuming the population is distributed approximately normally, and using the 0.05 level of significance, will the agent’s suspicion be confirmed?