# Math Help - confidence interval

1. ## confidence interval

Hi everyone,

A 95% confidenceinterval for the mean price of apartments is 752 to 798. Assume this result is based on a sample size of 100 and that the researchers knew the population standard deviation.

c. What is the margin of error for this confidence interval?

d. what is the value of the population standard deviation used to form this confidence interval?

Could someone please explain to me how to do these problems?

Thank you very much

2. You should have a confidence interval formula.

Another helpful formula would be the Sample Size: $n\;=\;\frac{z^{2}s^{2}}{d^{2}}$

Plug in the parts that are given.
Look up the z-score.
Solve for what is left.