Chapter 12.1, Problem 6E

Probability Table, Expected Value The number of phone calls coming into a telephone switchboard during each minute was recorded during an entire hour. During $30$ of the $1$-minute intervals there were no calls, during $20$ intervals there was one call, and during $10$ intervals there were two calls. A $1$-minute interval is to be selected at random and the number of calls noted. Let $X$ be the outcome. Then, $X$ is a random variable taking on the values $0,1,$ and $2$.

Write out a probability table for $X$.

Compute $3\left(X\right)$

Interpret $3\left(X\right)$