The manager of the zoo claims that the time spent by the visitors in the zoo is 90 minutes. A random sample of 16 visitors who went to the zoo produced the average time of 1.4 hour with a standard dev

The manager of the zoo claims that the time spent by the visitors in the zoo is 90 minutes. A random sample of 16 visitors who went to the zoo produced the average time of 1.4 hour with a standard deviation of 15 minutes. Assuming the spending time by the visitors have a normal distribution and using the 5% significance level, test whether the average time spending in the zoo is not 90 minutes