引用第0樓vincent於2011-09-22 22:49發表的“(each重賞500好友元)Stat QuestionsX6[趕急]”:
A student is getting ready to take an important oral exam and is concerned about her possibility of having an 'on' day or an 'off' day. She figures that if she has an 'on' day, then each of her examinars will pass her, independent of each other, with probability 0.8; whereas if she has an 'off' day, this probability will be reduced to 0.4. Supposethat the student will pass the examination if a majority of examinars pass her. If the student feels that she is twice as likely to have an 'off' day as she is to have an 'on' day, should she request an examination with 3 examinars or with 5 examinars?
2.俾左moment generating function,問你點搵expectation同variance,應該notes有大大條formula
4.probability加埋=1,咁就搵到k,expectation 同 variance用番原本條式就做到