[Exer4-3] Exercise 28 of Book {Devore2017B} P.117
The pmf for $X=$ the number of major defects on a randomly selected appliance of a certain type is
| $x$ | 0 | 1 | 2 | 3 | 4 |
| $p(x)$ | .08 | .15 | .45 | .27 | .05 |
Compute the following:
- (a) $E(X)$
- (b) $V(X)$ directly from the definition
- (c) The standard deviation of $X$
- (d) $V(X)$ using the shortcut formula