假設注射某疫苗的人有不良反應的機率為 0.001,求 2,000 人中
(1) 恰有 3 人 , (2) 超過 2 人 注射後有不良反應的機率。
因為:n = 2,000, p = 0.001 期望值(平均值)E(X)=λ=np= 2,000 ×0.001 = 2
(1) P ( x = 3 ) = (2^3e^-2)/3! = 0.180
(2) P ( x> 2) = 1 – {P ( x = 0 ) +P ( x = 1 ) +P ( x = 2 )} = 1 – ( 0.135 + 0.271 +
0.271) =1-0.677=0.323
抽樣數 |
不良率 |
發生次 |
期望值E(X) |
=POISSON |
=POISSON |
n |
p |
k |
λ |
=POISSON |
=1-POISSON |
2000 |
0.001 |
0 |
2 |
13.5335% |
86.4665% |
2000 |
0.001 |
1 |
2 |
27.0671% |
59.3994% |
2000 |
0.001 |
2 |
2 |
27.0671% |
32.3324% |
2000 |
0.001 |
3 |
2 |
18.0447% |
14.2877% |
2000 |
0.001 |
4 |
2 |
9.0224% |
5.2653% |
2000 |
0.001 |
5 |
2 |
3.6089% |
1.6564% |
2000 |
0.001 |
6 |
2 |
1.2030% |
0.4534% |
2000 |
0.001 |
7 |
2 |
0.3437% |
0.1097% |
2000 |
0.001 |
8 |
2 |
0.0859% |
0.0237% |
2000 |
0.001 |
9 |
2 |
0.0191% |
0.0046% |
2000 |
0.001 |
10 |
2 |
0.0038% |
0.0008% |
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