Re: Fisher-Freeman-Halton Exact Test or Jonckheere–Terpstra test - which is the most appropriate?
Posted by DP_Sydney on Feb 17, 2016; 12:18am
URL: http://spssx-discussion.165.s1.nabble.com/Fisher-Freeman-Halton-Exact-Test-or-Jonckheere-Terpstra-test-which-is-the-most-appropriate-tp5731524p5731538.html
I have performed Spearman Rank Correlations for both tests using a one-tailed hypothesis as I expect a priori that birds with more heavily pigmented tails will also have more heavily pigmented wings or forenecks.
The following graph shows a scatterplot of the data. As ordinal variables are used there are many duplicates of particular combinations of X-Y values. So the data points have been converted to different sized circles representing the number of individuals (i.e. sample size for that particular X-Y combination) as follows:
WING (= MANUS, top): 1 (smallest circle), 2-4, 5-9, 14, 20 (largest circle)
FORENECK (bottom): 1 (smallest), 2, 3, 4, 9 (largest)
Note "R6" in the x-axis title indicates the outer feather of the TAIL.
Results of the Spearman Rank Correlations are:
Wing: ρ = 0.193, t78 = 1.74, P = 0.043
Foreneck: ρ = 0.432, t38 = 2.95, P = 0.003
Calculating Pearson's Correlations for the data (for the sake of this thread):
Wing: r = 0.193, t78 = 1.73, P = 0.044
Foreneck: r = 0.3949, t38 = 2.65, P = 0.006
The results are very similar, including both correlation coefficient, test statistic and P value. The one exception is for the foreneck ρ > r, which according to comments in this post suggests the relationship may not be linear.
Given the data are ordinal scores I consider the Spearman Rank Correlation more appropriate to report.
NOTE: Two-tailed P-values are significant only for Foreneck. But THIS WAS NOT a deciding factor in calculating one-tailed tests a priori.
NOTE: the intervals used for the ordinal scores for the tail and foreneck are reasonably evenly spaced (i.e. the increase in level of pigmentation between adjacent scores is similar across all adjacent scores, EXCEPT for the first two scores for the tail which are much more similar to one another). The manus score is less 'evenly spaced'.
URL: http://spssx-discussion.165.s1.nabble.com/Fisher-Freeman-Halton-Exact-Test-or-Jonckheere-Terpstra-test-which-is-the-most-appropriate-tp5731524p5731538.html
I have performed Spearman Rank Correlations for both tests using a one-tailed hypothesis as I expect a priori that birds with more heavily pigmented tails will also have more heavily pigmented wings or forenecks.
The following graph shows a scatterplot of the data. As ordinal variables are used there are many duplicates of particular combinations of X-Y values. So the data points have been converted to different sized circles representing the number of individuals (i.e. sample size for that particular X-Y combination) as follows:
WING (= MANUS, top): 1 (smallest circle), 2-4, 5-9, 14, 20 (largest circle)
FORENECK (bottom): 1 (smallest), 2, 3, 4, 9 (largest)
Note "R6" in the x-axis title indicates the outer feather of the TAIL.
Results of the Spearman Rank Correlations are:
Wing: ρ = 0.193, t78 = 1.74, P = 0.043
Foreneck: ρ = 0.432, t38 = 2.95, P = 0.003
Calculating Pearson's Correlations for the data (for the sake of this thread):
Wing: r = 0.193, t78 = 1.73, P = 0.044
Foreneck: r = 0.3949, t38 = 2.65, P = 0.006
The results are very similar, including both correlation coefficient, test statistic and P value. The one exception is for the foreneck ρ > r, which according to comments in this post suggests the relationship may not be linear.
Given the data are ordinal scores I consider the Spearman Rank Correlation more appropriate to report.
NOTE: Two-tailed P-values are significant only for Foreneck. But THIS WAS NOT a deciding factor in calculating one-tailed tests a priori.
NOTE: the intervals used for the ordinal scores for the tail and foreneck are reasonably evenly spaced (i.e. the increase in level of pigmentation between adjacent scores is similar across all adjacent scores, EXCEPT for the first two scores for the tail which are much more similar to one another). The manus score is less 'evenly spaced'.
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