Independent solution

How to solve this Joint Distributions question

Setup

Setup

Let M be the larger of the two independent discrete risk levels and express the capped benefit through M.

M=max(X,Y),B=min(50M,100)M=\max(X,Y),\qquad B=\min(50M,100)

Model

Model

Since each ordered pair in the five-by-five grid is equally likely, count the pairs that place the maximum in each benefit tier.

Pr(B=0)=Pr(M=0)=125\Pr(B=0)=\Pr(M=0)=\frac1{25}
Pr(B=50)=Pr(M=1)=221225=325\Pr(B=50)=\Pr(M=1)=\frac{2^2-1^2}{25}=\frac3{25}
Pr(B=100)=1425=2125\Pr(B=100)=1-\frac4{25}=\frac{21}{25}

Compute

Compute

Weight each benefit level by its probability.

E[B]=0(125)+50(325)+100(2125)=90\operatorname{E}[B]=0\left(\frac1{25}\right)+50\left(\frac3{25}\right)+100\left(\frac{21}{25}\right)=90

Answer

Answer

The expected capped benefit is 90.

90(B)\boxed{90\quad\text{(B)}}