Question 670665
A survey of 36 "iPhone" owners showed that the purchase price has a sample mean of $450 with a sample standard deviation of $175. 
a) Compute the 95% confidence interval for the mean.
x-bar = 450
ME = 1.96*175/sqrt(6) = 9.5278
----
95%CI: 450-9.5278 < u < 450+9.5278
-------------------------------------------
b) How large a sample is needed to estimate the population mean within $10 at a 99% confidence level? 
n = [z*s/E]^2
------
n = [2.5758*175/10]^2 = 2032 when rounded up
-------------------------------------------------------
Cheers,
Stan H.