Friedman test on JMP?

[#1]

Dear all,

I am fairly new in using the JMP software, and as far as I can see there is no function in the programme for using the Friedman test? I have a non-normal distribution of my different sets of values (more than three groups) and is opting for a non-parametric test. That is, I had like to test a 2-way type of test (as ANOVA). Wilcoxon test is insufficient since it is a one-way test.

Do anybody know how I will deal with is problem? Is there another test to perform instead of Friedman test?

Best regards,

[#2]

Yes, a limitation of the Friedman test and ANY test with blocking is that the blocking variable does not interact with the factor.

To expand on this, suppose you have 10 blocks and 3 treatments. With the Friedman approach you are calculating ranks within each block. The ranks within each block will always add to 6. Therefore, when you conduct the testing there will not be any difference between the blocks (sums of squares will be 0 for the block effect).

If you DID put in an interaction (which you could try within JMP, you just need to use Fit Model instead of Fit Y by X), you would have 9 DF for the blocks, 2 DF for the treatment, and 18 DF for the interaction. You have 0 DF left for error. You have a saturated model and no testing would be available.