# [R] general question on binomial test / sign test

Kay Cecil Cichini Kay.Cichini at uibk.ac.at
Thu Sep 2 09:41:17 CEST 2010

```i test the null that the coin is fair (p(succ) = p(fail) = 0.5) with
one trail and get a p-value of 1. actually i want to proof the
alternative H that the estimate is different from 0.5, what certainly
can not be aproven here. but in reverse the p-value of 1 says that i
can 100% sure that the estimate of 0.5 is true (??) - that's the point
that astonishes me.

thanks if anybody could clarify this for me,
kay

Zitat von Greg Snow <Greg.Snow at imail.org>:

> Try thinking this one through from first principles, you are
> essentially saying that your null hypothesis is that you are
> flipping a fair coin and you want to do a 2-tailed test.  You then
> flip the coin exactly once, what do you expect to happen?  The
> p-value of 1 just means that what you saw was perfectly consistent
> with what is predicted to happen flipping a single time.
>
> Does that help?
>
> If not, please explain what you mean a little better.
>
> --
> Gregory (Greg) L. Snow Ph.D.
> Statistical Data Center
> Intermountain Healthcare
> greg.snow at imail.org
> 801.408.8111
>
>
>> -----Original Message-----
>> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
>> project.org] On Behalf Of Kay Cichini
>> Sent: Wednesday, September 01, 2010 3:06 PM
>> To: r-help at r-project.org
>> Subject: [R] general question on binomial test / sign test
>>
>>
>> hello,
>>
>> i did several binomial tests and noticed for one sparse dataset that
>> binom.test(1,1,0.5) gives a p-value of 1 for the null, what i can't
>> quite
>> grasp. that would say that the a prob of 1/2 has p-value of 0 ?? - i
>> must be
>> wrong but can't figure out the right interpretation..
>>
>> best,
>> kay
>>
>>
>>
>>
>>
>> -----
>> ------------------------
>> Kay Cichini
>> Institute of Botany
>> Univ. of Innsbruck
>> ------------------------
>>
>> --
>> View this message in context: http://r.789695.n4.nabble.com/general-
>> question-on-binomial-test-sign-test-tp2419965p2419965.html
>> Sent from the R help mailing list archive at Nabble.com.
>>
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