Independent solution

How to solve this Conditional Distributions question

Answer in brief

First average the conditional low-cost probabilities over the market states to obtain 0.32. The complementary high-cost probability is 0.68, so the expected cost is 5(0.32)+10(0.68)=8.4 million, choice D.

Setup

Setup

Use the market-state probabilities to remove the conditioning from the two-point cost distribution.

Pr(C=5)=sPr(C=5S=s)Pr(S=s)\Pr(C=5)=\sum_s \Pr(C=5\mid S=s)\Pr(S=s)

Model

Model

Weight each conditional low-cost probability by its corresponding market-state probability.

Pr(C=5)=0.05(0.10)+0.10(0.25)+0.25(0.30)+0.50(0.25)+0.90(0.10)\Pr(C=5)=0.05(0.10)+0.10(0.25)+0.25(0.30)+0.50(0.25)+0.90(0.10)

Compute

Compute

Complete the marginal cost distribution and take its expectation, in millions.

Pr(C=5)=0.32,Pr(C=10)=0.68\Pr(C=5)=0.32,\qquad \Pr(C=10)=0.68
E[C]=5(0.32)+10(0.68)=8.4\mathbb{E}[C]=5(0.32)+10(0.68)=8.4

Answer

Answer

The expected recall cost is 8.4 million.

E[C]=8.4 million(D)\boxed{\mathbb{E}[C]=8.4\text{ million}\quad\text{(D)}}