微软笔试第8道选择题

Let's assume one type of cancer may be mis-diagnosed in the examination. 5 out of 100 people with this cancer will be diagnosed as not having it , and 1 out of 100 people without this cancer will be diagnosed as having it. We know the chance of getting this cancer is around 0.1%. One person was examined and diagnosed of having this cancer, which of the following value if the closest to the chance of is really having it?(5 Points)

A、90%
B、50%
C、30%
D、10%

解析：

已知这种病的患病概率为0.01%，也就是说1000人中有1人患病

(1)1人患病：

0.95人被诊断出来，0.05人没有被诊断出来

(2)999人未患病：

9.99人被诊断出来，989，01人没有被诊断出来

则共有10.94人被诊断出来，其中真正患病的是0.95人，比率接近10%

则选D