印象中有回过, 却找不到... 前两天太累了, 可能回到一半就放弃或者因中断而被清掉? ※ 引述《[email protected] (要来念请慎重考虑)》之铭言： > 其实我不知道该去哪里问...因为是实验法的题目 > 好像又不属於统计的范畴@@" 而且看到指数对数就很头痛 >//////< 你没学过统计? 那要怎麽讲? > 所以想请教大家 给我一些指引 :) > 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" 是甚麽? p.d.f.? 那怎会有 "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" 是甚麽? 不知道的话去看看 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? 其实这题目的假设有问题. 设定上参数 λ 在 0-1 之间, 不含 0. 那麽 prior 设定 P[0<λ<1] = 1/10^6, 要如何去处理不 同 λ 值的问题? 既然在 prior 及报酬函数都只考虑 simple vs. simple 的检定问题, 就应设定单一 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 假说检定问题,这小题只不过是把 概度比表示的弃却域变成用 x 表示罢了! 只是, 题目却设定非单一的 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? 甚麽东西 "=1/8"? > 我很努力的想 也只可能知道第一提可能的解答是什麽 > 我会再努力看看 也希望板上的大家可以给我一点指引.. > 真的很感谢你们^^ -- H E L P !!! 统 计 专 业 版 需 要 你 !!! 来 贴 文 吧 !!! 无名小站 telnet://wretch.twbbs.org Statistics (统计方法讨论区) 成大计中站 telnet://bbs.ncku.edu.tw Statistics (统计方法及学理讨论区) 盈月与繁星 telnet://ms.twbbs.org Statistics (统计：让数字说话) 交大资讯次世代 telnet://bs2.twbbs.org Statistics (统计与机率) ★本文未经本人同意请勿转载; 回覆请勿全文引用, 请仅留下直接涉及部分。 -- 夫兵者不祥之器物或恶之故有道者不处君子居则贵左用兵则贵右兵者不祥之器非君子 之器不得已而用之恬淡为上胜而不美而美之者是乐杀人夫乐杀人者则不可得志於天下 矣吉事尚左凶事尚右偏将军居左上将军居右言以丧礼处之杀人之众以哀悲泣之战胜以 丧礼处之道常无名朴虽小天下莫能臣侯王若能守之万物将自宾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将知止知止可以不殆譬道之在天 163.15.188.87海