A sample of 64 was taken from a population, with the mean of the sample being 119 and the standard deviation of the sample being 16. What is the 68% confidence interval for the mean of the population?

A. (115, 123)
B. (113, 125)
C. (117, 121)
D. (118, 120)

Question

A sample of 64 was taken from a population, with the mean of the sample being 119 and the standard deviation of the sample being 16. What is the 68% confidence interval for the mean of the population?

A. (115, 123)
B. (113, 125)
C. (117, 121)
D. (118, 120)

rational · Answer

68% is within 1 sigma of mean, so simply find the standard error and work the confidence interval

rational · Answer

standard error = 16/sqrt(64) = 16/8 = 2

rational · Answer

therefore the confidence interval would be 2 units away from mean  :
$$(119-2,~~119+2) ~~~= ~~~(117,~~121)$$