Question

A simple random sample of 90 is drawn from a normally distributed population, and the mean is found to be 138, with a standard deviation of 34. What is the 90% confidence interval for the population mean? Use the table below to help you answer the question.

Confidence Level
90%
95%
99%
z*-score
1.645
1.96
2.58

Answer 1

90% = mean ± 1.645 SEm

SEm = SD/√n

Answer 2

132.10 to 143.90