# RE: st: probability question

 From To Subject RE: st: probability question Date Wed, 28 Oct 2009 10:08:31 -0400

```Isn't the probability of the client wearing a hat 4/120?

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of
vmz@vol.net.mt
Sent: October 28, 2009 9:59 AM
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: probability question

the probability that it rains on a given day is 7/120.The probability
that it rains on three given days is [7/120]^3.The probability that the
client is wearing a hat is 3/4.The probability that it rains on three
given days and that the client is wearing a hat is [[7/120]^3] * 3/4  =
00014887,the way I see it.

n 28/10/2009, "Richard Williams" <Richard.A.Williams.5@ND.edu> wrote:

>At 08:22 AM 10/28/2009, Jeph Herrin wrote:
>
>>Prob(rain) = 7/120
>>Prob(no rain) = 113/120
>>
>>X=days it rains on hat
>>
>>Prob(X=3)=c(4,3)*(7/120)^3*(113/120)^1
>>           =4*0.0001985*0.94
>>           =0.0007477
>>
>>
>>not much chance!
>
>Don't the probabilities change though?  e.g. if it rains on the first
>day, then the probability of rain on the 2nd day is 6/119.
>
>Maybe Maarten can just run a couple million simulations for us...
>
>
>-------------------------------------------
>Richard Williams, Notre Dame Dept of Sociology
>OFFICE: (574)631-6668, (574)631-6463
>HOME:   (574)289-5227
>EMAIL:  Richard.A.Williams.5@ND.Edu
>WWW:    http://www.nd.edu/~rwilliam
>
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```