試題詳解

199. An insurance company studies back injury claims from a manufacturing company. The insurance company finds that 40% of workers do no lifting on the job, 50% do moderate lifting and 10% do heavy lifting.

During a given year, the probability of filing a claim is 0.05 for a worker who does no lifting, 0.08 for a worker who does moderate lifting and 0.20 for a worker who does heavy lifting.

A worker is chosen randomly from among those who have filed a back injury claim.

Calculate the probability that the worker’s job involves moderate or heavy lifting.
(A) 0.75
(B) 0.81
(C) 0.85
(D) 0.86
(E) 0.89