Question

Verify that the functions are probability mass functions, and determine the requested probabilities.

Answer 1

Answer:

a) 3/64 = 0.046 (4.6%)

b) 63/64 = 0.9843 (98.43%)

c) 1/64 = 0.015 (1.5%)

d) 1/4 = 0.25 (25%)

Step-by-step explanation:

in order to verify that the f(x) is a probability mass function , then it should comply the requirement that the sum of probabilities over the entire space of x is equal to 1. Then

∑f(x)*Δx = 1

if f(x)=(3/4)(1/4)^x , x = 0, 1, 2, ...

then Δx=1 and

∑f(x) = (3/4)∑(1/4)^x = (3/4)* [ 1/(1-1/4)] = (3/4)*(4/3) = 1

then f represents a probability mass function

a) P(X = 2)= f(x=2) = (3/4)(1/4)^2 = 3/64 = 0.046 (4.6%)

b) P(X ≤ 2) = ∑f(x) =  f(x=0)+ f(x=1) + f(x=2) = (3/4) + (3/4)(1/4) +  3/64 = 63/64 = 0.9843 (98.43%)

c) P(X > 2)= 1- P(X ≤ 2) = 1 - 63/64 = 1/64 = 0.015 (1.5%)

d) P(X ≥ 1) = 1 - P(X < 1) = 1 - f(x=0) = 1- 3/4 = 1/4 = 0.25 (25%)