Suppose you have obtained a confidence interval for μ,but wish to obtain a greater degree of precision.Which of the following would result in a narrower confidence interval?
I.Increasing the sample size while keeping the confidence level fixed
II.Decreasing the sample size while keeping the confidence level fixed
III.Increasing the confidence level while keeping the sample size fixed
IV.Decreasing the confidence level while keeping the sample size fixed

Question

Suppose you have obtained a confidence interval for μ,but wish to obtain a greater degree of precision.Which of the following would result in a narrower confidence interval? 
I.Increasing the sample size while keeping the confidence level fixed
II.Decreasing the sample size while keeping the confidence level fixed
III.Increasing the confidence level while keeping the sample size fixed
IV.Decreasing the confidence level while keeping the sample size fixed

Quizplus · Accepted Answer

Increasing the sample size (I) decreases the standard error, which narrows the confidence interval. Decreasing the confidence level (IV) reduces the critical value (z or t), which also narrows the interval.

Suppose You Have Obtained a Confidence Interval for μ,But Wish