posted by Sandy on .
A simple random sample of 120 SAT scores ahs a mean of 1540. Assume that SAT scores have a population standard deviation of 333.
a) Construct a 95% conf. interval estimate of the mean SAT score.
b) Is a 99% conf. interval estimate of the mean SAT score wider than the 95% conf. interval estimate you got from part (a)? Why?
95% = mean ± 1.96 SEm
SEm = SD/√n
99% = mean ± 2.575 SEm
This should allow you to answer the questions.