Consider the following probability distribution. The variance is _____.
A) 1.14
B) 1.29
C) 1.65
D) 1.94

Question

Consider the following probability distribution.  The variance is _____.
A) 1.14 
B) 1.29 
C) 1.65 
D) 1.94

Quizplus · Accepted Answer

The formula for variance is Var(X) = E(X^2) - [E(X)]^2. 
Using the table, we can find that: 
E(X) = 1(0.20) + 2(0.25) + 3(0.35) + 4(0.15) + 5(0.05) = 2.90
E(X^2) = 1^2(0.20) + 2^2(0.25) + 3^2(0.35) + 4^2(0.15) + 5^2(0.05) = 10.10
Therefore, Var(X) = 10.10 - (2.90)^2 = 1.29. 
So the correct choice is B.

Consider the Following Probability Distribution