32. You plan to construct a confidence interval for the mean μ of a Normal population with (known) standard deviation σ. Which of the following will reduce the size of the margin of error?

A. Use a lower level of confidence.
B. Increase the sample size.
C. Reduce σ.
D. All of the above.

Question

32.	You plan to construct a confidence interval for the mean μ of a Normal population with (known) standard deviation σ. Which of the following will reduce the size of the margin of error?
	
A.	Use a lower level of confidence.
B.	Increase the sample size.
C.	Reduce σ.
D.	All of the above.

anonymous · Answer

http://www.troll.me/images/x-all-the-things/answer-all-the-questions-with-all-the-above.jpg

anonymous · Answer

please dont give up on me

anonymous · Answer

Remember what our margin of error would be here: $ME_\bar{x}=z^*\sigma$, where $z^*$ is our critical value, dependent on our confidence interval, and $\sigma$ our population standard deviation. Notice that since we know our population standard deviation, we don't need to estimate it using standard error and have no regard for sample size, so C is eliminated (and consequently so is D). Reducing the standard deviation would work although it seems impractical... the answer is likely A, as reducing our confidence level pulls our confidence interval closer around our sample mean, i.e. narrowing our margin of error.

anonymous · Answer

thank you for not giving up :)