# Calculation of mean and variance of a discrete random variable

1. Suppose that a variable x has the following distribution function:

x p(x)

3 0.23

5 0.41

9 0.36

What is the population mean?

2. Suppose that a variable x has the following distribution function:

x p(x)

1 0.18

6 0.16

9 0.15

24 0.51

What is F(9)?

3. Suppose that a variable x has the following distribution function:

x p(x)

1 0.19

5 0.15

8 0.66

What is the population variance?

4. Suppose that a variable x has the following distribution function: x p(x) 3 0.23 5 0.41 9 0.36 What is the expected value of (X - mean of x)^2?

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