ask a easy probability question

hinchun34

a choir group has 80 people, they need to choose 20 people for a new group, someone who  calls Patrick said he wanted  to join with his friend. what is the probability
i haven't learnt it so i don't know whether there is about the structute wrong

hinchun34

because we haven't learnt it yet
and u would know who the teacher is

secret

Mr Patrick:
Why don't you ask your teacher why the problem should be solved in such
an Out-C way? (curious)

hinchun34

ok
ic
overall it is taught by my teacher
i don't know it

sapphire

原帖由 hinchun34 於 5/5/2006 15:41 發表
yes u ar correct
the answer is told by my teacher
his solution is
78C18
-------
80C20
0.06013(4sig. fig.)

78C18/80C20 的是AL Applied Math的計算方法吧,印象中CE是不能用這方法的......

hinchun34

yes u ar correct
the answer is told by my teacher
his solution is
78C18
-------
80C20
0.06013(4sig. fig.)

[ 本帖最後由 hinchun34 於 5/5/2006 15:43 編輯 ]

細薯

原帖由 kazuhiko 於 5/5/2006 15:07 發表


得一個group 咋嘛

ar......i wrongly thought that the 80 ppl form 4 groups of each 20 ppl...==
oic...then that should be 19/316..

kazuhiko

原帖由 hinchun34 於 4/5/2006 16:36 發表
a choir group has 80 people, they need to choose 20 people fora new group, someone who  calls Patrick said he wanted  to join with his friend. what is the probability
i haven't learnt it so i don ...

得一個group 咋嘛

細薯

原帖由 kazuhiko 於 5/5/2006 14:54 發表


做咩要乘四？

80 ppl -> 4 groups
P(both in group 1) = (1/4)(1/4)=1/16
P(both in group 2) = (1/4)(1/4)=1/16
P(both in group 3) = (1/4)(1/4)=1/16
P(both in group 4) = (1/4)(1/4)=1/16

P(both in the same group) = (1/16)(4)=1/4

correct ma....

原帖由 kazuhiko 於 5/5/2006 14:54 發表


做咩要乘四？

應該係
Required probobility
= (20/80) x (19/79)
=19/316

then.....
(19/316)(4) =0=
i don't know....-__-

[ 本帖最後由 細薯 於 5/5/2006 15:00 編輯 ]

kazuhiko

原帖由 細薯 於 5/5/2006 14:46 發表

not this mei....?

(20/80)(20/80)(4)=1/4

@@

做咩要乘四？

應該係
Required probobility
= (20/80) x (19/79)
=19/316

[ 本帖最後由 kazuhiko 於 5/5/2006 14:57 編輯 ]