Answer:
The value of the standardized z-test statistic is -6.4.
Explanation:
The test statistic is:
In which X is the sample mean,
is the value tested at the null hypothesis, and s is the standard error.
0.28 is tested at the null hypothesis:
This means that
p ^ 0.216 with SE 0.01
This means that
Then
The value of the standardized z-test statistic is -6.4.