[R] Test for trend?

Strecker, Stefan Stefan.Strecker at iw.uni-karlsruhe.de
Wed May 28 11:17:43 CEST 2003

Hello R community,

I would like to test for learning effects by subjects in my experiment. Each subject participates in six consecutive auction rounds of the same treatment.
The response variable is the efficiency of an auction outcome measured by a real number. Since the efficiency increases over the six rounds, I suppose that subjects learn about the rules of the auction institution, but I would like to test for that conjecture. 

The prop.trend.test does not seem to be right, because the treatment does not change between the rounds, i.e. the number of trials (n) is not available. A linear regression shows a positive slope and the 99%-confidence interval shows a significant deviation from a zero slope, but I am not able to compute the exact p-value. The Cox-Stuart test for trend detects a trend but gives a p-value of 1.

Isn't there a distribution-free, exact test for trend which operates on the rank-oder of the data instead of binary coded values?

Please apologize for asking a rather R-unspecific question.

Thanks in advance
Stefan Strecker
Universitaet Karlsruhe (TH)
Department of Economics and Business Engineering
Chair for Information Management and Systems
Englerstrasse 14
D-76131 Karlsruhe, Germany
T: +49 721 608 8374
F: +49 721 608 8399
M: +49 179 69 29 746
DH PGP Key available upon request

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