Suppose that the random variable X is equal to the number of hits obtained by a certain baseball player in this next 3 at bats.
If P(X =1) = 0.3, P(X = 2) = 0.2, and P(X = 0) = 3P(X = 3).
Find:
1. the pmf of X.
2. the expectation of X.
3. the variance of X.
4. the standard devaition of X.