A simple random sample of 60 items resulted in a sample mean of 96. The population standard deviation is 16.

Question

a. Compute the 95% confidence interval for the population mean (to 1 decimal).
( , )

b. Assume that the same sample mean was obtained from a sample of 120 items. Provide a 95% confidence interval for the population mean (to 2 decimals).
( , )

c. What is the effect of a larger sample size on the margin of error, does it increase, decrease,stays the same, or it cannot be determined?

Answer 1

I'll get you started.

a) CI95 = mean ± 1.96 (sd/√n)

mean = 96
sd = 16
n = 60

b) Use the same formula, except n = 120

c) Compare the margin of error in a) and b) to answer this question.