At a Particular Academically Challenging High School, the Average GPA

Multiple Choice

At a particular academically challenging high school, the average GPA of a high school senior is known to be normally distributed. After a sample of 20 seniors is taken, the average GPA is found to be 2.71 and the variance is determined to be 0.25. Find a 90% confidence interval for the population mean GPA.

A) [2.5167, 2.9033]
B) [2.5261, 2.8961]
C) [2.5615, 2.8585]
D) [2.6358, 2.7842]