In a study of 200 students, 42 were found to have a GPA greater than 3.0. Find a

98% confidence interval estimate of the proportion, p, of all students that have a GPA greater than 3.0.

1 answer

CI98 = p ± 2.33 √(pq/n)

p = 42/200 = .21
q = 1 - p = 1 - .21 = .79
n = 200

With your data:

CI98 = .21 + 2.33 √[(.21)(.79)/200]

I'll let you take it from here to finish.