Question

A field test for a new exam was given to randomly selected seniors. The exams were graded, and the sample mean and sample standard deviation were calculated. Based on the results, the exam creator claims that on the same exam, nine times out of ten, seniors will have an average score within 5% of 75%. Is the confidence interval at 90%, 95%, or 99%? What is the margin of error? Calculate the confidence interval and explain what it means in terms of the situation.

Answer 1

the confidence interval is 90 % 0.05 < p < 0.75

and margin of error is 35 %

Explanation:

Since 9 out of 10 students is 90 % so the confidence interval is 90 %

Range of Confidence Interval = 2* ME where ME = Margin of Error

0.75 - 0.05 = 2* ME

0.7 = 2 * ME

0.7 / 2 = ME

0.35 = ME or

ME = 35 %