印象中有回過, 卻找不到... 前兩天太累了, 可能回到一半就放棄或者因中斷而被清掉? ※ 引述《[email protected] (要來唸請慎重考慮)》之銘言： > 其實我不知道該去哪裡問...因為是實驗法的題目 > 好像又不屬於統計的範疇@@" 而且看到指數對數就很頭痛 >//////< 你沒學過統計? 那要怎麼講? > 所以想請教大家 給我一些指引 :) > Suppose a gang of smugglers were trying illegally to export radioactive > material.In an effort to try to stop this, you monitor with a Geiger > counter every package leaving the country. > For those packages without the radioactive material (NRA) > the number of counts is given approximately by an exponential > distribution. > Letting x equal the number of counts: > f(x|NRA) = λe^(-x) "f" 是甚麼? p.d.f.? 那怎會有 "λ"? > For the package with radio active material (RA) > f(x|RA) = λe^(-λx) 0 < λ < 1.00 > (a) What is the likelihood ratio of a package’s containing radioactive > material as opposed to its not containing radioactive material? "likelihood ratio" 是甚麼? 不知道的話去看看 mathematical statistics 的教本吧! > (b) If the a priori probability of a package’s containing radioactive > material is 1 in 10^6 , and if > $100 is cost of opening a package and repacking it if does not contain > radioactive material (false alarm -$100) > $10^4 is value of catching a radioactive package (Hit +$10^4) > $10^6 is cost of letting a radioactive package through (Miss -$10^6) > $0 is the value of letting a nonradioactive package through > (correct rejection +$0) > What value of likelihood ratio should lead one to ask that the package > be opened? 其實這題目的假設有問題. 設定上參數 λ 在 0-1 之間, 不含 0. 那麼 prior 設定 P[0<λ<1] = 1/10^6, 要如何去處理不 同 λ 值的問題? 既然在 prior 及報酬函數都只考慮 simple vs. simple 的檢定問題, 就應設定單一 λ 值. > (c) If =1/6, what value of x would one need to attain that value of > likelihood ratio in (b)? 在 simple vs. simple 假說檢定問題,這小題只不過是把 概度比表示的棄卻域變成用 x 表示罷了! 只是, 題目卻設定非單一的 λ 值... > Suppose your budge director gives you $300,000 per year, so that you can > afford to open 3000 packages per year even if none is radioactive. > (d) What number of counts would you use on the assumption that 10 > packages are processed each year? 看不懂... > (e) What is your probability of detecting a radioactive package if=1/8? 甚麼東西 "=1/8"? > 我很努力的想 也只可能知道第一提可能的解答是什麼 > 我會再努力看看 也希望板上的大家可以給我一點指引.. > 真的很感謝你們^^ -- H E L P !!! 統 計 專 業 版 需 要 你 !!! 來 貼 文 吧 !!! 無名小站 telnet://wretch.twbbs.org Statistics (統計方法討論區) 成大計中站 telnet://bbs.ncku.edu.tw Statistics (統計方法及學理討論區) 盈月與繁星 telnet://ms.twbbs.org Statistics (統計：讓數字說話) 交大資訊次世代 telnet://bs2.twbbs.org Statistics (統計與機率) ★本文未經本人同意請勿轉載; 回覆請勿全文引用, 請僅留下直接涉及部分。 -- 夫兵者不祥之器物或惡之故有道者不處君子居則貴左用兵則貴右兵者不祥之器非君子 之器不得已而用之恬淡為上勝而不美而美之者是樂殺人夫樂殺人者則不可得志於天下 矣吉事尚左凶事尚右偏將軍居左上將軍居右言以喪禮處之殺人之眾以哀悲泣之戰勝以 喪禮處之道常無名樸雖小天下莫能臣侯王若能守之萬物將自賓天地相合以降甘露民莫 之令而自均始制有名名亦既有夫亦將知止知止可以不殆譬道之在天 163.15.188.87海