唔好介意我用英文回你
Let X be the random variable representing the number of chickens infected
(a)1-0.05-0.95x0.05-095x0.95x0.05-0.95x0.95x0.95x0.05
=0.81450625
(b) X~B(5,0.05)
5C3 x 0.05x0.05x0.05 x 0.95x0.95
=0.001128125 作者: syms5104 時間: 2016-1-11 10:59 PM
2 LET X and Y be the random variable representing the number of signals emitted by beacon A and B per 15 minutes respectively
X~Po(2)
Y~Po(1.5)
the required probabillity
=P(X=0)x P(Y=3)+ P(X=1) x P(Y=2) + P(X=2) x P( Y=1)+ P(X=3) x P(Y=0)
=0.215785469 作者: syms5104 時間: 2016-1-11 11:13 PM
3 Let X be the random variable representing the number of questions that are correctly answered
(a) X~B(6,0.7)
The required probability
15(6x0.7)+10
=73
(b) X~G(0.7)
The required probability
0.3x0.3x0.3x0.7
=0.01789
(c)
The required probability
P(X=0)+P(X=1)+P(X=2)+P(X=3)+P(X=4)
=0.579825 作者: brianlok547 時間: 2016-1-12 02:23 AM
1(a)最少5次=頭4次要抽唔到
Let X be random variable representing infected chickens.
P(X>=5)
=1-P(X<=4)
=1-P(X=1)-P(X=2)-P(X=3)-P(X=4)
=1-0.05-0.05(0.95)-0.05(0.95)ˆ2-0.05(0.95ˆ3
(b)5隻雞入邊要有3隻=binomial distribution
P(X=3)
=5C3 (0.05)ˆ3 (0.95)ˆ2