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標 題[問題]gamma distribution
發信站無名小站 (Sun Apr 20 16:42:01 2008)
轉信站ptt!Group.NCTU!grouppost!Group.NCTU!wretch
As part of a grand opening promotion, a department store has advertised that
every 1000th purchase made on opening day will be given to the customer for
free. The store expects 5 purchases to be made every minute. Let X be the
time (in minutes) from opening until the first free purchase is given away.
Ans: X ~ Gamma(a, l) with a=1000 and l=5. (An alternative answer that is
acceptable is Exponential(l) with l=1/(1000/5)=1/200.)
答案
X ~ Gamma(a, l) with a=1000 and l=5
是以1人0.2分鐘來看
請問若我以5人為一單位
那麼X~Gamma(200,1)
但為什麼不行呢？
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◆ From: 123.195.50.65
1F：→ HERMAN06:以5個人為單位時 每個單位應該是服從 Gamma(5,5)04/18 23:01
2F：→ algebra1029:對啊 5人單位 並不服從 Exp(1) 而是服從 Gamma (5,5)04/18 23:19
3F：→ Arton0306:抱歉 還是不懂 5人為一單位 那X表一單位要等幾分鐘04/19 12:53
4F：→ Arton0306:為何X~Exp(1)是不對的？？ 04/19 12:54
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