An Educator Wanted to Look at the Study Habits of University

Multiple Choice

An educator wanted to look at the study habits of university students. As part of the research, data was collected for three variables - the amount of time (in hours per week) spent studying, the amount of time (in hours per week) spent playing video games and the GPA - for a sample of 20 male university students. As part of the research, a 95% confidence interval for the average GPA of all male university students was calculated to be: (2.95, 3.10) . Which of the following statements is true?

A) In construction of the confidence interval, a z-value was used.
B) In construction of the confidence interval, a z-value with 20 degrees of freedom was used.
C) In construction of the confidence interval, a t-value with 19 degrees of freedom was used.
D) In construction of the confidence interval, a t-value with 20 degrees of freedom was used.