$X$ takes the values 0, 1 and 2 with probabilities 0.3, 0.5 and 0.2. What is $E(X)$?

Explanation

1. 01

   $E(X) = \sum x\,P(X = x) = 0 \times 0.3 + 1 \times 0.5 + 2 \times 0.2$.

2. 02

   $= 0.5 + 0.4 = 0.9$.