Posted by peter on .
average commuting distance 10.9 miles which is also the mean of a sample of 300 commuters. Sample sd is 6.2 miles . Estimate the true mean using 99% confidence please.

statistics 
PsyDAG,
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability ([1.99]/2) and its Z score.
99% = mean ± Z(SEm)
SEm = SD/√n