Question

A field test for a new exam was given to randomly selected freshmen. 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 6% of 80%.

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.

I know that the z score is 1.645 because the confidence level is 90%. But I am lost on the rest of the problem

Answer 1

The margin of error is the distance between the center of a confidence interval to the end of the interval. Six percent of 80% is 80 * 0.06 = 4.8%. Therefore the confidence interval is ((80 - 4.8)%, (80 + 4.8)%).
The exam creator has used statistics from a random sample of freshmen to calculate the confidence interval for average scores for seniors. The result is not likely to be valid.

Answer 2

Thank you so much! But I am lost for the margin of error

Answer 3

The margin of error is six percent of 80%, which is 80 * 0.06 = 4.8%.

Answer 4

And I also have another question that I need help on.. If you are interested in helping a girl out lol :)

Answer 5

Oh! okay! I get it now ! thank you so much

Answer 6

You're welcome :)
I'll try to help with another. Please post as a new question. Thanks.