Question

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?

Answer 1

a) 95% = mean ± 1.96 SD

b) 95% = mean ± 1.96 SEm

SEm = SD/√(n-1)

c) margin of error decreases.

Answer 2

I would really like to know this answer, i am not good at doing the calculations....can someone help please?

Answer 3

How do you get 1.96