Because we are given a small sample size of
n = 25,
it is not appropriate to use the z statistic. Instead, we can use the t statistic if two criteria are met: the sample must be randomly selected, and the population must be normally distributed. It is given that both of these conditions are met, so we can use the t statistic for this test.
Recall the formula for the test statistic t.
t =
x − 0
s

n

It is given that
x = 69.8,

s = 15,
and
n = 25.
The value of
0
is the population mean we are testing against, which is given as = 72. Substitute these values into the formula to calculate t, rounding to three decimal places.
t =
x − 0
s

n



=
69.8 −
72

Correct: Your answer is correct.
15

25



=

Incorrect: Your answer is incorrect.