A simple random sample of size n is drawn from a population that is normally distributed. The samplemean, x, is found to be 109, and the sample standarddeviation, s, is found to be 10.

(a) Construct a 90% confidence interval about if the samplesize, n, is 20.

(b) Construct a 90% confidence interval about if the samplesize, n, is 15.

How does decreasing the sample size affect the margin oferror, E?

A.

As the sample size decreases, the margin of error stays the same.

B.

As the sample size decreases, the margin of error decreases.

C.

As the sample size decreases, the margin of error increases.

(c) Construct a 70% confidence interval about if the samplesize, n, is 20.

Compare the results to those obtained in part(a). How does decreasing the level of confidence affect the size of the margin oferror, E?

A.

As the level of confidence decreases, the size of the interval stays the same.

B.

As the level of confidence decreases, the size of the interval decreases.

C.

As the level of confidence decreases, the size of the interval increases

(d) Could we have computed the confidence intervals in parts(a)-(c) if the population had not been normallydistributed?

A.

Yes, the population needs to be normally distributed.

B.

No, the population does not need to be normally distributed.

C.

No, the population needs to be normally distributed.

D.

Yes, the population does not need to be normally distributed.