As part of a project about response bias, Ellery surveyed a random sample of 25 students from her school. One of the questions in the survey required students to state their GPA aloud. Based on the responses, Ellery said she was 90% confident that the interval from 3.14 to 3.52 captures the mean GPA for all students at her school. Required:
a. Interpret the confidence level.
b. Explain what would happen to the length of the interval if the confidence level were increased to 99%.
c. How would a 90% confidence interval based on a sample of size 200 compare to the original 90% interval?
d. Describe one potential source of bias in Ellery's study that is not accounted for by the margin of error.