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.

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.

carolinar7 · Answer

@mathway

jchick · Answer

the exam creator claims that on the same exam, nine times out of ten, seniors will have an average score within 6% of 80%.

jchick · Answer

that means Confidence Interval is 90%

jchick · Answer

9 / 10 means 90 / 100 so, the Confidence Interval is 90% accurate

jchick · Answer

confidence interval = 80%±6%

jchick · Answer

so "Margin of Error" is 6%

jchick · Answer

in interval notation, confidence interval = (74%, 86%)

jchick · Answer

Do you understand what I have done here?

jchick · Answer

Does this make sense?