Question

If we change a 95% confidence interval estimate to a 99% confidence interval estimate, we can expect

	A.	the required sample size to increase
	B.	the UCL - LCL range to decrease
	C.	precision of the estimate to decrease
	D.	precision of the estimate to increase

Answer 1

For a greater confidence level, the critical z value increases, and thus the margin of error also increases. The confidence level itself dont have any relation to the sample size.

Lower confidence level, decreases the margin of error and therefore the width of the confidence interval also become narrower. Therefore the precision also increases with lower confidence level. As we increase the confidence level to 99% here, therefore the margin of error increases, interval width widens and hence the precision decreases.

Therefore C is the correct answer here.