An airline institutes a "snake system" waiting line at its counters to try to reduce the average waiting time. The mean waiting time under specific conditions with the previous system was 6.1 minutes. A sample of 16 waiting lines is taken; the times are measured at widely separated times to eliminate the possibility of dependent observations. The resulting sample mean is 5.7 and the standard deviation is 1.3. Test the null hypothesis of no change against an appropriate research hypothesis using =.05. Assume that the population of waiting times is approximately normal.

What is the appropriate test to perform?

• t-test about mean.H₀:=6.1 versus H_a:6.1
• z-test about mean.H₀:=6.1 versus H_a:>6.1
• z-test about mean.H₀:=6.1 versus H_a:<6.1
• z-test about proportion.H₀:p<6.1 versus H_a: p=6.1
• t-test about mean.H₀:<6.1 versus H_a:=6.1
• z-test about proportion.H₀:p=6.1 versus H_a: p>6.1
• z-test about mean.H₀:=6.1 versus H_a:6.1
• t-test about mean.H₀:=6.1 versus H_a: <6.1

A manufacturer of cookies and crackers does a small survey of the age at sale of one of its brands. A random sample of 64 retail markets in a particular region is chosen. In each store, the number of days since manufacture of the frontmost box of crackers is determined by date code on the box. The samples mean is 56.7 and the standard deviation is 30. Can we infer at the 1% significance level that the true mean age is less than 60?

What is the appropriate test to perform?

• t-test about mean.H₀:=56.7versus H_a:<56.7
• z-test about mean.H₀:=60 versus H_a:60
• z-test about mean.H₀:=60 versus H_a: <60
• t-test about mean.H₀:=60 versus H_a:<60
• z-test about proportion.H₀:p=60 versus H_a: p>60
• z-test about mean.H₀:=56.7versus H_a:<56.7
• z-test about proportion.H₀:p=60 versus H_a: p60
• t-test about mean.H₀:=60 versus H_a:>60