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Population Mean = Expected Value E(X) (Q1b)

Another term for the mean is the Expected Value of X or E(X)

For a discrete probability distribution, the mean is NOT calculated as:

…Instead, the probabilities of each x must be included in the formula for the expected value of X as follows:

Expected Value of X

Order of operations is very important here:

1st » Brackets: … no operations within brackets in this formula…

2nd » Exponents: … no exponents in this formula…

3rd » Division: … no division in this formula…

4th » Multiplication: X x P(x) « multiplication symbol normally hidden

5th » Addition: ΣXP(x)

6th » Subtraction: … no subtraction in this formula


Test your understanding: