[理工] [機率] 排列組合
there are three types of animals in a laboratory:15 type I
13 type II &12 type III.Animals of type I react to a particlar
stimulus in 5 sec ,type II and type III react to the same
stimulue in 4.5 sec and 6.2 sec, respectively.A psychologist
selects 10 of these animals at random and finds the a exactly
four of them react to this stimulus in 6.2 sec.What is the
prob that at least two of them react to the same stimulus
in 4.5 sec.
我的想法是
B = 至少兩隻type II
A = 十隻有四隻type III
_
P(B│A) = 1 - P(B│A)
12 13 15 12 15
P C C + P C
4 1 5 4 6
=1 - ──────── * 6! (請問這樣列有錯嗎?)
40
P
10
Ans: 0.8831(我跟算的跟答案不一樣 我不知道是我哪列錯 還是計算機按錯?)
===========================================================================
12 13 15 12 15
C C C + C C
4 1 5 4 6
=1 - ───────── 不考慮順序的話 改成這樣 也跟答案不同
40 為什麼??
C
10
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◆ From: 220.129.38.177
推
09/27 23:00, , 1F
09/27 23:00, 1F
→
09/27 23:08, , 2F
09/27 23:08, 2F
※ 編輯: lai90043 來自: 220.129.38.177 (09/27 23:10)
→
09/28 00:18, , 3F
09/28 00:18, 3F
→
09/28 00:19, , 4F
09/28 00:19, 4F
推
09/28 01:41, , 5F
09/28 01:41, 5F
→
09/28 01:42, , 6F
09/28 01:42, 6F
→
09/28 01:44, , 7F
09/28 01:44, 7F
→
09/28 01:45, , 8F
09/28 01:45, 8F
→
09/28 08:45, , 9F
09/28 08:45, 9F
※ 編輯: lai90043 來自: 220.129.35.110 (09/28 09:26)
→
09/28 11:29, , 10F
09/28 11:29, 10F
→
09/28 11:32, , 11F
09/28 11:32, 11F
→
09/30 23:27, , 12F
09/30 23:27, 12F
討論串 (同標題文章)