Page "Expected value" Paragraph 8

... = p < sub > k </ sub >), then the weighted average turns into the simple average.

This is intuitive: the expected value of a random variable is the average of all values it can take ; thus the expected value is what you expect to happen on average.

If the outcomes x < sub > i </ sub > are not equiprobable, then the simple average ought to be replaced with the weighted average, which takes into account the fact that some outcomes are more likely than the others.

The intuition however remains the same: the expected value of X is what you expect to happen on average.