On Sat, 16 Dec 2006, R. Villegas wrote:
2006/12/15, Carmen Meier <[EMAIL PROTECTED]>:
Hello r-group
I have a question to the ks.test.
I would expect different values for less and greater between data1 and
data2.
Does anybody could explain my point of misunderstanding the function?
The help page says:
This is a comparison of cumulative distribution
functions, and the test statistic is the maximum difference in
value, with the statistic in the '"greater"' alternative being D^+
= max_u [ F_x(u) - F_y(u) ].
data1 and data2 have the same empirical CDF, so should and do give the
same value of the test statistic.
We cannot know what you misunderstanding is, since you have not explained
your expectations.
data1<-c(8,12,43,70)
data2<- c(70,43,12,8)
ks.test(data1,"pnorm")
ks.test(data1,"pnorm",alternative ="less") #expected < 0.001
ks.test(data1,"pnorm",alternative ="greater") #expected =1
ks.test(data2,"pnorm")
ks.test(data2,"pnorm",alternative ="less") #expected =1
ks.test(data2,"pnorm",alternative ="greater") #expected < 0.001
With regards Carmen
Possible you are unable to use the KolmogorovÿÿSmirnov test given that
the sample size is small.
You can: the distribution theory is exact.
--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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