作者s911125 (江小LO)
看板Grad-ProbAsk
标题[问题] 94北科统计2题
时间Tue Mar 24 20:52:45 2009
1.a computer,in adding numbers,rounds each number off to the nearest integer.
suppose that all rounding errors are independent and unformly distributed over
(-0.5,0.5).if 1500 numbers are added,what is the probability that the
magnitude of the total error exceeds 15 ?
A. 0.1802
b. 0.3132
c. 0.0451
d. 0.2842
我的算法是这样 X~U(-0.5,0.5) E(X)=0 V(X)=1/12
Y=X(1)+X(2)+++++X(1500) E(X)=0 V(X)=1500*(1/12)=125
P(Y>15)=P(Z>(15-0)/125^1/2)=P(Z>1.34)=0.0918
请问是哪边观念错了?
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1F：推 loveliver:这题应该是考总和型CLT 03/24 21:31
2F：→ disroxen:我跟原PO算一样的答案，请问该如何解呢? 03/25 00:31