作者DIDIMIN ( )
看板Grad-ProbAsk
标题Re: [商管] [统计]-normal p.d.f
时间Wed Feb 3 23:51:17 2010
※ 引述《Nocp (冲浪..被浪冲 傻傻分不清)》之铭言：
: Show that the constant C can be selected so that
: f(x) = C*2^ -x^2 , -∞ < x < ∞ , satisfies the conditions
: of a normal p.d.f . Hint write 2 = e ^ln2
: 请问 这是不是超过商统了... 700题里!都没看见= =
Given f(x) is a normal distribution, we can use the property
∞
∫ f(x)dx = 1
-∞
to find the constant C.
∞
∫ C exp(-x^2 ㏑2)dx = 1 → C = (㏑2 / π)^0.5
-∞
So, if C = (㏑2 / π)^0.5, then f(x) satisfies the nornal distribution
with mean 0 and variance 1/2㏑2.
--
※ 发信站: 批踢踢实业坊(ptt.cc)
◆ From: 140.127.219.174
1F：→ NCUflywind:我算出来C=(ln2/π)^0.5 E(X)=0 Var(X)=1/2ln2 02/04 00:19
2F：→ NCUflywind:今天跟补习班老师确认过答案了~π前面没有2哦~~~ 02/05 00:33
※ 编辑: DIDIMIN 来自: 140.127.200.211 (02/05 11:50)