The probability mass function of a discrete random variable

The probability mass function of a discrete random variable X is defined as p(x) = x/10 for x = 0,1,2,3,4. Then, the value of the cumulative distribution function F(x) at x= 3 is:

a.) 0.10

b.) 0.30

c.) 0.60

d.) 0.90

Solution

F(3) = P(0) + P(1) + P(2) + P(3)

= 0/10 + 1/10 + 2/10+ 3/10

= 6/10

= 0.60 [OPTION C, ANSWER]