| To: | "SPLUS_NEWS" <s-news@lists.biostat.wustl.edu> |
|---|---|
| Subject: | Kolmogorov-Smirnov test for nested alternatives? |
| From: | "Bill Shipley" <bill.shipley@usherbrooke.ca> |
| Date: | Tue, 21 Feb 2006 10:06:53 -0500 |
| Importance: | Normal |
|
Hello. The
Kolmogorov-Smirnov test in S-PLUS allows one to test for a significant deviation
of an empirical distribution from a predicted distribution. Consider a
case where one has a series of nested alternative predicted distributions -
alternative exponential distributions with increasing numbers of estimated
parameters:
p(i)
=(1/Z)exp(-lamda0 -lambda1*t_i1-lamda2*t_i2...) where Z is a normalization
constant and t_i1 etc are attributes of each group i and the lamda coefficients
are estimated from the empirical data.
I would like to
conduct a series of sequential tests in which
(I)
I compare an
empirical distribution of proportions over a set of groups to the predicted
distributions assuming (1) all lamda values greater than 0 (i.e. lamda1, lamda 2
etc.) are zero; (2)all lamda values greater that 1 (i.e. lamda2, lamda3
etc.) are zero
(II) Compare the
improvement in fit as I increase the number of lamda values that are freely
estimated in order to detect non-significant improvement in
fit.
Is it possible to do
step (ii) using a Kolmogorov-Smirnov procedure?
Bill
Shipley |
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