Question

Consider the following discrete probability mass function.

x 3 1 –1
P(X = x) 0.25 0.30 0.45

Find P(X ≥ 1).

Answer 1

`P(x \geq 1) = 0.55`

Explanation:

Given:

x --------------3 ---------1 ------- –1

P(X = x) --- 0.25 ---0.30 ---- 0.45

Required

Calculate
`P(x \geq 1)`

`x \geq 1` implies that x = 1,2,3,4......

So:

`P(x \geq 1) = P(x = 1) + P(x = 3)`

From the above table

`P(x = 1) = 0.30`

`P(x = 3) = 0.25`

Substitute these values in
`P(x \geq 1) = P(x = 1) + P(x = 3)`

`P(x \geq 1) = 0.30 + 0.25`

`P(x \geq 1) = 0.55`