Determine Whether the Following Is a Probability Distribution

Short Answer

Determine whether the following is a probability distribution. If not, identify the requirement that is not satisfied.
-In a certain town, 50% of adults have a college degree. The accompanying table describes the probability distribution for the number of adults (among 4 randomly selected adults) who have a college degree.
$$\begin{array} { r | r } \mathrm { x } & \mathrm { P } ( \mathrm { x } ) \\\hline 0 & 0.0625 \\1 & 0.2500 \\2 & 0.3750 \\3 & 0.2500 \\4 & 0.0625\end{array}$$