Given X~B(n,p),E(X)=11.5 and Var(X)=8.855
1.Find the value of n and p,
2.FindP(10≤ X≤ 13),hence the mode of X
Probability?
2016-12-31 5:01 pm
回答 (1)
2016-12-31 9:01 pm
✔ 最佳答案
1.E(X) = n p = 11.5
V(X) = n p ( 1 - p ) = 8.855
1 - p = 8.855 / 11.5 = 0.77
p = 1 - 0.77 = 0.23
n = 11.5 / p = 11.5 / 0.23 = 50
Ans: n = 50 , p = 0.23
2.
P( 10 ≤ X ≤ 13 )
= P( (10-11.5)/√8.855 ≤ Z ≤ (13-11.5)/√8.855 )
= P( - 0.5 ≤ Z ≤ 0.5 )
= 1 - 2*P( Z < - 0.5 )
= 1 - 2*0.3085
= 0.383 ..... Ans
收錄日期: 2021-05-02 14:21:21
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https://hk.answers.yahoo.com/question/index?qid=20161231090129AACriXA