It was reported that average age of graduate students at a certain university is 27 years. To test this claim, a random sample of size 20 ages of graduate students was selected. The computed sample...

 It was reported that average age of graduate students at a certain university is 27 years. To test this claim, a random sample of size 20 ages of graduate students was selected. The computed sample mean and sample standard deviation were 25 and 7 years, respectively.

a.

The value of the test statistic is

b.
If the test is to be conducted at 1% significance level, the rejection region is

c.

At 1% significance level, we can claim that the average age of graduate students on this particular university campus is