-------- Original Message -------- Subject: Question about the interpretation of results from the PLS within configuration function in MorphoJ Date: Tue, 8 Nov 2011 15:07:11 -0500 From: Jana Makedonska <[email protected]> To: [email protected] Dear morphometricians, I am a MorphoJ user trying the interpret within-configuration PLS results. I would greatly appreciate your opinion on my interpretation of the meaning of the singular values and correlation coefficients, especially in situations in which the singular value is significant, but the between-block correlation is not. Please let me know if my reasoning with regard to the meaning of the variables and their associated significance tests makes sense. Each singular value expresses the amount of squared between-block covariance that it contains, which can also be expressed as a percentage of total squared covariance contained in the data. It is determined by the strength of association between the two blocks and by the variance contained in the PLS axes of the two blocks. The between-block correlation coefficient indicates the extent to which scores in one block can predict scores in the other block. Thus, the correlation coefficient only measures the strength of association between the specimens' SVD scores for the two blocks. Significance tests for singular values are different from significance tests for correlation coefficients. The test for the significance of the singular values must be a permutation test which destroys the existing covariance between the block, but what is its exact nature? The significance test for the correlation coefficient must be a resampling test in which the individual SVD scores from block 1 are randomly matched with scores of individuals from block 2 (?). Thanks in advance for your help! Regards, Jana ([email protected] <mailto:[email protected]>) -- "The world is full of mysteries. Life is one. The curious limitations of finite minds are another."(J.B.S. Haldane, The Causes of Evolution) Jana Makedonska, M.Sc. Ph.D. candidate/ Part-time lecturer Department of Anthropology College of Arts & Sciences State University of New York at Albany 1400 Washington Avenue 12222 Albany, NY Office phone: 518-442-4699
