Re: [理工] [機率]-機率

[bonn00 (蹦)]

※ 引述《AAJJBurnett (叫我投手)》之銘言：
:  A store sells four brands of VCRs.The least expensive brand B1 accounts
:  for 40% of the sales. The other brands(in order of their price) have the
:  following percentages of sales:B2,30%;B3,20%;and B4,10%.The respective
:  probabilities of needing repair during warranty are 0.10 for B1,0.05 for
:  B2, 0.03 for B3, and 0.02 for B4. A randomly selected purchaser has a VCR
:  that needed repair under warranty. What are the four conditional
:  probabilities of being brand Bi, i=1,2,3,4 ?

令Y為送修事件

              0.10, i=1
              0.05, i=2
P（Y｜Bi）=   0.03, i=3
              0.02, i=4

         0.4, i=1
         0.3, i=2
且P(Bi)= 0.2, i=3
         0.1, i=4

可依序得，P（Y╭╮B1）=0.10*0.4=0.04 ...etc

將得到的四個機率總合，可得到P(Y)

而　　P(Y╭╮B1）
     ------------ = P(B1｜Y)....此求法得依序得其它條件機率。
         P(Y)


有錯請指教, 謝謝~　

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