Independent solution

How to solve this Discrete Random Variables question

Setup

Setup

For each surcharge level, identify the event that its corresponding year is the most recent accident year.

Pr(J=j)=0.1(0.9)j,j=0,1,2,3\Pr(J=j)=0.1(0.9)^j,\qquad j=0,1,2,3

Model

Model

Multiply each mutually exclusive event probability by its surcharge rate.

E[R]=0.20(0.1)+0.15(0.1)(0.9)+0.10(0.1)(0.9)2+0.05(0.1)(0.9)3\operatorname{E}[R]=0.20(0.1)+0.15(0.1)(0.9)+0.10(0.1)(0.9)^2+0.05(0.1)(0.9)^3

Compute

Compute

Add the four expected-rate contributions.

E[R]=0.020000+0.013500+0.008100+0.003645\operatorname{E}[R]=0.020000+0.013500+0.008100+0.003645
E[R]=0.045245=4.5245%\operatorname{E}[R]=0.045245=4.5245\%

Answer

Answer

The expected surcharge rounds to 4.5%.

4.5%(A)\boxed{4.5\%\quad\text{(A)}}