1 - 0.07 = 0.93 (probability of an individual blood sample testing negative for the virus)
0.93 x 0.93 x 0.93 x 0.93 x 0.93 = 0.6957 (probability of all 5 individual samples are negative)
1 - 0.6957 = 0.3043 (as long as 1 individual sample is positive,all 5 will be positive)
这题其实是很基础的统计学应用题.首先要懂得题意.如果五个取样混合都是阴性,那么 我们知道五个样本单独都是阴性.换句话说,只要五个样本单独有一个是阳性,那么五个取样混合就会是阳性.所以要解这题,首先要找出五个人全部都是阴性的几率,然后用100%减去全部阴性的几率,就得到其中任何一个或几个是阳性的几率了.