NO.PZ2024120401000002
问题如下：
Credit card companies rapidly assess transactions for fraud. In each day, a large card issuer assesses 10,000,000 transactions. Of these, 0.001% are fraudulent. If their algorithm identifies 90% of all fraudulent transactions but also 0.0001% of legitimate transactions, what is the probability that a transaction is fraudulent if it has been flagged?
选项：
A.
10%
B.
50%
C.
70%
D.
90%
解释：
We are interested in Pr(Fraud|Flag). This value is Pr(Fraud x Flag)/Pr(Flag). The probability that a transaction is flagged is 0.001% * 90% + 99.999% * 0.0001% = 0.000999%.
The Pr(Fraud x Flag) = 0.001% * 90% = 0.0009%. Combining these values, 0.0009% / 0.000999% = 90%.
这道题没有看懂，请老师解释一下，谢谢
