In constructing a 95 percent confidence interval, if you increase n to 4n, the width of your confidence interval will be (assuming other things remain the same):
A)about 25 percent of its former width.
B)about two times wider.
C)about 50 percent of its former width.
D)about four times wider.

Question

Quizplus · Accepted Answer

As n increases, the width of the confidence interval decreases as the sample mean becomes a more precise estimate of the population mean. Thus, multiplying n by 4 will result in a width that is approximately 1/4 of its former width (or 25% of its former width). Therefore, the correct answer is choice C.

In Constructing a 95 Percent Confidence Interval, If You Increase