Question

A random sample of 121 automobiles traveling on an interstate showed an average speed of 65 mph. From past information, it is known that the standard deviation of the population is 22 mph. The standard error of the mean is

Answer 1

Answer: 2.

Explanation:

Number of samples = 121

Average speed (sample mean) = 65mph

Population standard deviation = 22 mph

The standard error of the mean is:

Standard error of the mean(S.Em)

Standard error of the mean is the proportion of the population standard deviation and the square root of the sample size.

S.Em = standard deviation / √same size

S.Em = 22 / √121

S.Em = 22 / 11

S.Em = 2