A random sample of 64 observations has a mean of 20, a median of 21, and a mode of 22. The population standard deviation is known to equal 4.8. The 95.44% confidence interval for the population mean is
A) 15.2 to 24.8.
B) 18.8 to 21.2.
C) 18.986 to 21.014.
D) 21.2 to 22.8.

Question

Quizplus · Accepted Answer

The 95.44% confidence interval corresponds to approximately 2 standard deviations from the mean in a normal distribution. The standard error is 4.8/sqrt(64) = 0.6. Thus, the interval is 20 ± 2*0.6, which is 18.8 to 21.2.

A Random Sample of 64 Observations Has a Mean of 20