Question

A business school placement director wants to estimate the mean annual salaries 5 years after students graduate. A random sample of such graduates found a sample mean of $427,400. A confidence interval for the population mean annual salaries 5 years after students graduate is then estimated to be from $419,020 to $435,780. If the placement director considers that this confidence interval is too wide and would like to have an interval of half width only, what should he do?

Select one:

A. Keeping all others constant, decrease the sample size by half.

B. Keeping all others constant, reduce the confidence level by half.

C. None of the other choices.

D. Keeping all others constant, choose another sample with half sample mean.

Answer 1

Correct option is C. None of the other choices.

Explaination why option correct or not correct

A. Keeping all others constant, decrease the sample size by half..this is not correct answer because by doing this width will increase since width depends on margine of error

B. Keeping all others constant, reduce the confidence level by half.this is not correct answer because by doing this width will not decrease by half width

C. None of the other choices.This is correct option since others are not correct

D. Keeping all others constant, choose another sample with half sample mean.this is not correct answer because

width depends on margine of error it doesnt depend on sample mean.

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