?

Statistics and Probability

Free Version

Upgrade subject to access all content

Difficult

Finding Variance of a Sample Mean

STATS-RMIVGX

Suppose there is some population consisting of $100$ individuals where $98$ of the individuals are $25$ years old and $2$ individuals are $20$ years old.

The following facts can be shown to be true about a sample of size two that is to be collected from this population:

  • The probability that the sample will have two 25-year-olds is $.9602$

  • The probability that the sample will have one 25-year-old and one 20-year-old is $.0396$

  • The probability that the sample will have two 20-year-olds is $.0002$

    Let $X$ be the mean age of the sample. Find the variance of $X$.

A

$\$0$

B

$\$23$

C

$\$13$

D

$\$6.25$

E

$24.9$