In a sample of 171, the mean is 58 with a population standard deviation of 4.8. Can someone help me figure out what is the 90% confidence interval of the true mean? Thank you.
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the Z score for .4500 from mean (Z = 1.645)
90% conf. Interval = mean ± 1.645(SEm)
SEm (Standard Error of the mean) = SD/?(n-1)
There is a difference if you want to find confidence intervals for distribution of scores or distribution of means.