Question

The following table shows the probability distribution for a discrete random variable.

X 13 16 18 21 23 25 26 31
P(X) 0.07 0.21 0.17 0.25 0.05 0.04 0.13 0.08
The mean of the discrete random variable X is 20.59. What is the variance of X? Round your answer to the nearest hundredth.

Answer 1

First, subtract the mean from each number and square it: (x -mean)^2.
Write each of these numbers down.

Now, multiply each one of these numbers by the probability of that variable:
p(x) * (x-mean)^2.

Add these together and you have the variance.