Question

Find the mean and standard deviation of the following probability distribution:

x 1 2 3
P(x) 0.3 0.5 0.2

Answer 1

Your data:

X P(X)

1 0.3
2 0.5
3 0.2

Here's a formula for the mean:
SUM[X * P(X)]
(Take each X times its respective P(X), then sum for a total. This will be your mean.)

Here's a formula for the standard deviation:
SQRT of {SUM[X^2 * P(X)] - mean^2}
(Square each X. Take each X^2 times its respective P(X), then sum for a total. Subtract mean^2 from this value. Then take the square root of that result. This will be your standard deviation.)

I hope this will help get you started.