[R] ks.test troubles

[Uwe Ligges]

Martin Kaffanke wrote:
> Hi there!
> 
> I have two little different data.  One is a computer test on people, the
> other is a paper and pencil test.  two boxplots show me that the data is
> almost the same.
> 
> So now I'd like to know if I could handle all data as one, by testing
> with ks.test:
> 
> ====
>> ks.test(el$angststoer, fl$angststoer)
> 
>         Two-sample Kolmogorov-Smirnov test
> 
> data:  el$angststoer and fl$angststoer 
> D = 0.1413, p-value = 0.9112
> alternative hypothesis: two-sided 
> 
> Warning message:
> In ks.test(el$angststoer, fl$angststoer) :
>   cannot compute correct p-values with ties
> ====
> 
> Ok, so how can I get the p-value?


You already got it, it is 0.9112, but since you have ties in your data, 
R warns you about it (it's not an error, just a warning). And indeed, 
you have some ties in fl$angststoer.

Uwe Ligges



> I tried two tests:
> ====
>> ks.test(fl$angststoer, "dnorm")
> 
>         One-sample Kolmogorov-Smirnov test
> 
> data:  fl$angststoer 
> D = 0.8109, p-value < 2.2e-16
> alternative hypothesis: two-sided 
> 
> Warning message:
> In ks.test(fl$angststoer, "dnorm") :
>   cannot compute correct p-values with ties
> ====
> 
> so I see that this message in the first one, depends on fl$angststoer.
> 
> The I have on this two vectors:
> 
> ====
>> fl$angststoer
>  [1]  1.22184871 -0.30103000  1.00000000 -1.30103000  0.69897000
> -0.30103000
>  [7] -2.30103000 -1.00000000 -2.00000000  0.22184832 -1.77819468
> -0.30103000
> [13] -2.00000000 -0.30103000 -0.30103000  0.22184832 -0.90308999
> -1.14611935
> [19] -1.30103000 -3.20411998 -0.60205999 -2.25531594 -3.60205999
> -1.30103000
> [25] -2.30103000 -0.07918038 -2.14599777  0.74472745 -3.30103000
> -0.30103000
> [31] -0.30103000 -4.30103000 -0.60205999 -0.14612847 -1.30103000
> -1.30103000
> [37]  0.00000000 -0.17609234 -0.47711908 -1.77819468 -1.00000000
> -1.20411998
> [43] -0.07918038 -2.00000000 -2.00000000 -1.30103000
>> el$angststoer
>  [1] -2.2407100 -2.8601209 -0.5005659 -2.4007721 -0.3474336 -2.6653452
>  [7]  0.6548865 -1.6281751 -1.2940679 -0.1316566 -1.4541612 -1.6560206
> [13] -0.7441850  0.8219399  0.1746081 -1.2314248 -3.8910969  0.1328448
> [19] -1.8439508 -0.8833972 -0.4936052 -0.1664593 -0.8694749 -2.8253588
> ====
> 
> Doesn't seem to be a problem?
> 
> What can I do for a good computation?
> 
> Thanks,
> Martin
> 
> 
> 
> 
> 
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