$P(X = x) = \frac{x}{10}$ for $x = 1, 2, 3, 4$. What is $E(X)$?

Explanation

1. 01

   $E(X) = \sum x \cdot \frac{x}{10} = \frac{1 + 4 + 9 + 16}{10}$.

2. 02

   $= \frac{30}{10} = 3$.