Independent solution

How to solve this Cumulative Probabilities question

Answer in brief

Evaluating the loss CDF at the reimbursement limit gives probability 0.65 of full reimbursement and 0.35 of a partial shortfall. Independence makes the probability of two full reimbursements followed by a shortfall equal to 0.65 squared times 0.35, or 0.147875, so choice D is correct.

Setup

Setup

A loss is fully reimbursed exactly when it does not exceed the payment limit.

p=Pr(X0.80)=F(0.80)p=\Pr(X\le0.80)=F(0.80)

Model

Model

Evaluate the supplied CDF and use its complement for a partially unreimbursed loss.

p=0.80+15(0.80)216=0.65p=\frac{0.80+15(0.80)^2}{16}=0.65
q=1p=0.35q=1-p=0.35

Compute

Compute

The first shortfall occurs on the third event only when the first two are fully reimbursed and the third exceeds the limit.

Pr(T=3)=p2q\Pr(T=3)=p^2q
Pr(T=3)=(0.65)2(0.35)=0.147875\Pr(T=3)=(0.65)^2(0.35)=0.147875

Answer

Answer

The required probability rounds to 0.148.

0.148(D)\boxed{0.148\quad\text{(D)}}