If X is a normal random variable with a standard deviation of 10,then 3X has a standard deviation equal to
A)10.
B)13.
C)30.
D)90.

Question

Quizplus · Accepted Answer

The standard deviation of a random variable is directly proportional to the scale factor applied to it. Therefore, if X has a standard deviation of 10, then 3X (X scaled by a factor of 3) will have a standard deviation of 3 times 10, which equals 30.

If X Is a Normal Random Variable with a Standard