Question

PLEASE HELP I HAVE BEEN IGNORED FOR MY LAST SIMILAR 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 4% of 70%.

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

Do you think you could help me @ganeshie8 ?

Answer 2

Or @zepdrix ?

Answer 3

A 95% confidence interval for the population mean is an interval such that on average, 95 out of every 100 such intervals will contain the population mean.

Does this help you to make the correct choice of answer.

Answer 4

Sorry had to step away for a sec

Answer 5

Margin of Error is the distance between the center of a confidence interval to the end of the interval (a quantity half the width of the confidence interval).

Answer 6

So the confidence interval is 90%, but what would that be in this situation?

Answer 7

A 90% confidence interval for the population mean is an interval such that on average, 90 out of every 100 such intervals will contain the population mean.

Answer 8

What is 4% of 70%? That will give you the Margin of Error.

Answer 9

2.8%

Answer 10

Correct.

Answer 11

So my answer is the confidence interval is 90% and the margin of error is 2.8%. Thank you! This part always confuses me!

Answer 12

You're welcome :) The confidence interval is:
(70 - 2.8)%, (70 + 2.8)%

Answer 13

Also, thank you for helping so late at night :P

Answer 14

You're most welcome :)