Re: Fisher-Freeman-Halton Exact Test or Jonckheere–Terpstra test - which is the most appropriate?

Posted by DP_Sydney on Feb 16, 2016; 1:56am
URL: http://spssx-discussion.165.s1.nabble.com/Fisher-Freeman-Halton-Exact-Test-or-Jonckheere-Terpstra-test-which-is-the-most-appropriate-tp5731524p5731529.html

Hi Rich and Raimundas,

Thanks for the comments.

The total sample size for the two tests is 80 (tail vs wing) and 40 (tail vs foreneck). The marginal distributions for each test are shown in the graphs below.

These distributions are bell-shaped for Test 1, and unimodal with a positive skew for Test 2. So you've convinced me that it is more appropriate to run a rank correlation on the data, which is also more intuitive (i.e. a correlation).

WRT to the Jonckheeere-Terpstra test, Rich you wrote "The JT test does not handle ties well ... I have not used it, but quick reading suggests that having a continuous outcome (and small N) are two of the expectations." I would like to read the text you refer to (this test may come in useful in the future, so I'm keen to learn more). I have not read anything about continuous outcomes, indeed the first reading I did about the JT test refers to its use in doubly-ordered contingency tables - i.e. ordinal dependent & ordinal independent (http://www.sussex.ac.uk/its/pdfs/SPSS_Exact_Tests_21.pdf). I'm also unsure what you mean by "ties".

Thanks also for the advice regarding the lack of power of the FFH Exact Test through it ignoring the ordinal nature of the variables, something I didn't appreciate.  

Cheers,
Dean