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# RE: st: Which test to use?

 From "Seed, Paul" To "statalist@hsphsun2.harvard.edu" Subject RE: st: Which test to use? Date Fri, 20 May 2011 10:13:38 +0100

```Toby's data can be summarised as 3 frequencies using
-tabulate-.  (X==1 & Y==0; X==0 & Y==1 ;  X==0 & Y==0)
He can get CI for the percentages of these with a little ingenuity

He tells us that X and Y never occur together;
so his question (as asked) does not make much sense.
They are linked by definition, (as a chi-sq test will confirm),
and no test is needed.

Allowing for his English, a sensible question is
"Is X more common than Y?"

He can approach this by ignoring occasions when X and Y are the
same, using -bitest-.  If he has another question in mind,
perhaps he can explain further.

******* example code *********
tab X Y, cell
gen neither = X+Y == 0
ci X Y neither, bin
bitest X = 0.5 if X !=Y
******* end example code *****

On Thu, May 19, 2011 at 9:12 AM, Toby <spiegeldesaster@googlemail.com> wrote:
> Hello,
>
> I have data of the following character
>
>
> decision      X      Y
> 34               1      0
> 34               1      0
> 56               0      0
> 77               0      1
> 23               0      0
>
>
> X and Y take the function of categorizing the variable decision. If I
> take the mean value of X I get the frequency of decision that could be
> classifed as X, the same holds for Y. It could never be that X and Y
> take the value 1 at the same time.
> Now I want to test whether the frequency of X is significantly
> different from the frequency of Y. Can anybody help me figuring out
> which statistical test I have to use?

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```