Perform the Jonckheere-Terpstra test on trend.
There are situations in which treatments are ordered in some way, for example the increasing dosages of a drug. In these cases a test with the more specific alternative hypothesis that the population medians are ordered in a particular direction may be required. For example, the alternative hypothesis could be as follows: population median1 <= population median2 <= population median3. This is a one-tail test, and reversing the inequalities gives an analagous test in the opposite tail. Here, the Jonckheere-Terpstra test can be used. Bewick V., Cheek L., Ball J. Statistics review 10: further nonparametric methods. Critical Care 2004, 8: 196-199
Assumptions:

Data must be at least ordinal

Groups must be selected in a meaningful order i.e. ordered If you do not choose to enter your own group scores then scores are allocated uniformly (1 ... n) in order of selection of the n groups.

Created by Giuseppe Cardillo
giuseppe.cardillo-edta@poste.it

To cite this file, this would be an appropriate format: Cardillo G. (2008) Jonckheere-Terpstra test: A nonparametric Test for Trend http://www.mathworks.com/matlabcentral/fileexchange/22159