The average length of time customers spent on waiting at ABC Store’s check-out c

The average length of time customers spent on waiting at ABC Store’s check-out counter before a new P.O.S. system was installed was 5.1 minutes. A sample of 49 customers randomly selected at the check-out counter after the new P.O.S. system was installed showed that the average waiting time was 4.55 minutes with a sample standard deviation of 1.45 minutes. We wish to determine if there has been a significant decrease (from 5.1 minutes) in the average waiting time after the P.O.S. system was installed
1. State the null and alternative hypotheses to be tested?
2. Compute the test statistic?
3. Determine the critical value for this test at the 0.05 level of significance?
4. What do you conclude at the 0.05 level of significance? 
5. Construct a 95% confidence interval for the average waiting time after the new P.O.S. system was installed?

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