The cumulative distribution function Fx of a discrete random

The cumulative distribution function F(x) of a discrete random variable X is given by F(0) = .30, F(1) =0.70, F(2) = 0.90, and F(3) = 1.0, then the value of the probability mass function p(x) at x = 1 is.

A.) 0.30 B.) 0.40 C.) 0.20 D.) 0.80

Solution

see f(1) = 0.70

we have to find the p(x) at x=1 that will be f(x)/4

0.70/3 = 0.17 = 0.20 round off value