posted by TIMBERLY .
A simple random sample of 60 items resulted in a sample mean of 80. The population standard deviation is 15.
a) Compute the 95 % confidence interval for the population mean.
b) Assume that the same sample mean was obtained from a sample of 120 items. Provide a 95% confidence interval for the population mean.
c)What is the effect of a larger sample size on the margin of error?