Listed below are student evaluation ratings of courses, where a rating of 5 is f

Question

Listed below are student evaluation ratings of courses, where a rating of 5 is for "excellent." The ratings were obtained at one university in a state. Construct a confidence interval using a

90%

confidence level. What does the confidence interval tell about the population of all college students in the state?

3.9

3.1

3.7

4.4

3.2

4.1

3.3

4.4

4.3,

4.4

4.5

3.9

3.2

4.2,

4.0

USING EXCEL

What is the confidence interval for the population mean

mu?

What is the confidence interval for the population mean

mu?

<

(Round to two decimal places as needed.)

What does the confidence interval tell about the population of all college students in the state? Select the correct choice below and, if necessary, fill in the answer box(es) to complete your choice.

A.

The results tell nothing about the population of all college students in the state, since the sample is from only one university.

B.We are 90%

confident that the interval from

  to actually contains the true mean evaluation rating.

(Round to one decimal place as needed.)

C.

We are confident that

90%

of all students gave evaluation ratings between   

and .

(Round to one decimal place as needed.)

Explanation / Answer

Ans:

a)df=15-1=14

crirical t value for 90% CI is 1.76

Confidence interval of mean

=3.93+/-1.76*0.48/sqrt(15)

=3.93+/-0.22

=(3.71,4.15)

b)

We are 90% confident that the interval from 3.7 to 4.2 actually contains the true mean evaluation rating.

Option B is correct.

1 3.9 2 3.1 3 3.7 4 4.4 5 3.2 6 4.1 7 3.3 8 4.4 9 4.3 10 4.4 11 4.5 12 3.9 13 3.2 14 4.2 15 4 mean= 3.93 std dev= 0.48

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