问一道题：NO.PZ2020010301000009

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：

90%

80%

95%

10%

解释：

We are interested in Pr(Fraud|Flag). This value is Pr(Fraud $\cap$ Flag)/Pr(Flag). The probability that a transaction is flagged is

.001% * 90% + 99.999% * 0.0001% = .000999%.

The Pr(Fraud $\cap$ Flag) = .001% * 90% = .0009.

Combining these values,

.0009 /.000999 = 90%.

This indicates that 10% of the flagged transactions are not actually fraudulent.

请问这个数学运算怎么做的？我总是算不对

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1 个答案

品职答疑小助手雍 · 2020年08月19日

嗨，爱思考的PZer你好：

按数字数也不是不行，这10million的交易里，F的占100个，那L的就是9999900个。

算法标记的数量就是90%*100+9999900*0.0001%=90+9.9999=99.9999个。

现在一笔交易被标记了，那他是F的可能就是90/99.9999=90%

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就算太阳没有迎着我们而来，我们正在朝着它而去，加油！

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NO.PZ2020010301000009 问题如下 Cret carcompanies rapiy assess transactions for frau In eay, a large carissuer assesses 10,000,000 transactions. Of these, 0.001% are fraulent. If their algorithm intifies 90% of all fraulent transactions but also 0.0001% of legitimate transactions, whis the probability tha transaction is fraulent if it hbeen flagge A.90% B.80% C.95% 10% We are interestein Pr(FrauFlag). This value is Pr(Frau\cap∩Flag)/Pr(Flag). The probability tha transaction is flaggeis.001% * 90% + 99.999% * 0.0001% = .000999%.The Pr(Frau\cap∩Flag) = .001% * 90% = .0009.Combining these values,.0009 /.000999 = 90%.This incates th10% of the flaggetransactions are not actually fraulent. 画图法怎么画这道题，求解

2022-04-26 15:28 1 · 回答

老师能一下这道题的意思吗

2020-12-05 20:10 2 · 回答

请问这题的答案解析是不是写错了，按照贝叶斯公式变形后，frauflag在分子应该为交集而不是并集吧？

2020-02-18 01:11 1 · 回答

请问什么叫flagged

2020-02-04 09:25 1 · 回答

问一道题：NO.PZ2020010301000009

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