作者betray911015 (回头太难)
看板Statistics
标题[问题] 几题normal distribution
时间Thu Nov 26 18:24:03 2009
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1. If X is normally distributed with mean 2 and variance 2, express
P[∣X-1∣≦2] in terms of the standard normal cumulative distribution
function.
2 2
2. If X is normally distributed with mean μ>0 and variance σ = μ,
express P[ X < -μ∣X <μ] in terms of the standard normal cumulative
distribution function.
My answer:
1. P[∣X-1∣≦2] = P[-2≦X-1≦2] = P[-1≦X≦3]
= P[(-1-2)/√2≦Z≦(3-2)/√2]
= P[-3/√2≦X≦1/√2]
= 0.7611 -0.0422
= 0.7189
这是我算的第一题，但我这样不知是不是他所要求的答案
而第二题 P[ X<-μ∣X<μ]会等於 P[ X<-μ]吗??
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