Answer:
C) In construction of the confidence interval, a t-value with 19 degrees of freedom was used.
Step-by-step explanation:
When to use t or z distribution?
If we know the population standard deviation, we use the z distribution(find a z value related to the confidence level).
Otherwise, if we only have the sample standard deviation, the t-distribution is used.
In this problem, we have no information about the standard deviation of GPA for male university adults, just for the sample, so the t-distribution, and a respective t value is used.
To find a t-value, we also have to find our degrees of freedom. The degrees of freedom(df) is the sample size subtracted by 1.
For this interval, we have a sample of 20 students. So, we have 20-1 = 19 degrees of freedom.
So the correct answer is:
C) In construction of the confidence interval, a t-value with 19 degrees of freedom was used.
