stanford大學(xué)-大數(shù)據(jù)挖掘-introdu-在線瀏覽
2025-07-14 23:38本頁面
【正文】 nduct scientific research. 17 Stanford Professor Proves Tracking Terrorists Is Impossible! ?Three years ago, the example I am about to give you was picked up from my class slides by a reporter from the LA Times. ?Despite my talking to him at length, he was unable to grasp the point that the story was made up to illustrate Bonferroni’s Principle, and was not real. 18 The “TIA” Story ?Suppose we believe that certain groups of evildoers are meeting occasionally in hotels to plot doing evil. ?We want to find (unrelated) people who at least twice have stayed at the same hotel on the same day. 19 The Details ?109 people being tracked. ?1000 days. ?Each person stays in a hotel 1% of the time (10 days out of 1000). ?Hotels hold 100 people (so 105 hotels). ?If everyone behaves randomly (., no evildoers) will the data mining detect anything suspicious? 20 Calculations – (1) ?Probability that given persons p and q will be at the same hotel on given day d : ? 1/100 ? 1/100 ? 105 = 109. ?Probability that p and q will be at the same hotel on given days d1 and d2: ? 109 ? 109 = 1018. ?Pairs of days: ? 5?105. p at some hotel q at some hotel Same hotel 21 Calculations – (2) ?Probability that p and q will be at the same ho
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