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
Confidence Level
90%
95%
99%
z*-score
1.645
1.96
2.58
Answers
90% = mean ± 1.645 SEm
SEm = SD/√n
SEm = SD/√n
132.10 to 143.90
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