Independent solution

How to solve this Conditional Probability question

Setup

Setup

Translate the strict cost threshold into the allowed visit counts.

100N>350N4100N>350\quad\Longleftrightarrow\quad N\ge4

Model

Model

Form the conditional probability of exactly five visits within the qualifying tail.

Pr(N=5N4)=Pr(N=5)Pr(N=4)+Pr(N=5)+Pr(N=6)\Pr(N=5\mid N\ge4)=\frac{\Pr(N=5)}{\Pr(N=4)+\Pr(N=5)+\Pr(N=6)}

Compute

Compute

Insert the three relevant table masses and normalize.

Pr(N4)=0.04+0.02+0.01=0.07\Pr(N\ge4)=0.04+0.02+0.01=0.07
Pr(N=5N4)=0.020.07=0.2857143\Pr(N=5\mid N\ge4)=\frac{0.02}{0.07}=0.2857143

Answer

Answer

The conditional probability rounds to 0.286.

0.286(C)\boxed{0.286\quad\text{(C)}}