Question

please help
Find the mean and standard deviation of the following probability distribution:
x 1 2 3
P(x) 0.2 0.4 0.4

Answer 1

E[x] = 1*0.2 + 2*0.4 + 3*0.4 = Mean = First Moment
E[x^2] = 1*0.2 + 4*0.4 + 9*0.4 = Second Moment
Var(X) = ??? You tell me.
StdDev(X) = ???

Answer 2

thank you