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. The value of the cumulative distribution function F(x) at x = 3 is:

a) 0.30

b) 0.60

c) 0.90

d) 0.10

Solution

P(0) = 0

P(1) = 0.1

P(2) = 0.2

P(3) = 0.3

P(4) = 0.4

The cumulative distribution function F(x) at x = 3

= 0+0.1+0.2+0.3

= 0.60 Answer (B)