# Thread: Find mean and variance

1. ## Find mean and variance

Hello,
Two shots are fired independently at a target. The probability of hitting the target on each shot is p. The following two random variables are considered.

1. X, the difference between the number of hits and the number of misses,
2. Y, the total sum of the number of hits and number of misses.

Find for each an expression for mean and variance.

any help would be appreciated. Thanks.

2. Originally Posted by riptorn70
Hello,
Two shots are fired independently at a target. The probability of hitting the target on each shot is p. The following two random variables are considered.

1. X, the difference between the number of hits and the number of misses,
2. Y, the total sum of the number of hits and number of misses.
Find for each an expression for mean and variance.

any help would be appreciated. Thanks.
Construct a probability distribution table for X and Y and then calculate mean and variance in the usual way.