Yesterday's talk [Feb. 19, 2001], "DNA Fingerprinting," by the University of Chicago's Michael Linacre at the LSU HSC Dept of Genetics was attended by more than 25 people. Linacre presented a basic contrast of the differing purposes motivating the use of mathematical models in statistical and measurement research. He passed around a Ptolemaic astrolabe [courtesy of Tom O'Neill] as an illustrative artifact of the days when Ptolemy's descriptively superior account of the heavenly bodies was held also to be theoretically superior to the Copernican account. Most statistical studies of test, survey, and genetic data are similar to the Ptolemaic system in achieving accurate data description, but will eventually fall to theoretically superior measurement accounts that support enhanced predictive capacities, just as Ptolemy's system fell when confronted with Newton's laws of motion.
Mike then recapitulated his analysis of Geyer & Thompson's (1992) DNA fingerprinting data [RMT 7:1, 274], showing how a probabilistic conjoint (Rasch) measurement model for genetic diversity can provide a measure of relatedness. Mike also showed the results of his recent examination of data from a popular textbook comparing genetic frequencies across different global regions. In taking up this topic, with no prior knowledge of the personal connection or the work that was done, Mike cited a researcher (Morton) with whom Bronya Keats, Head of the Dept. of Genetics, had worked, and furthermore took the analysis in the same direction that Keats and Morton had 25 years previously when working with similar data. Of special interest in this work was the use of "lods," log-odds units, known in Rasch measurement as logits. After the seminar, Keats provided Linacre with reprints of the published work she did with Morton; these articles include tables of data which Linacre plans to evaluate in a Rasch context. Stay posted for a comparison of lods and logits ....
William P. Fisher, Jr.
Fisher, W.P. Jr. (2001) "DNA Fingerprinting" Redivivus. Rasch Measurement Transactions 14:4 p.785
"DNA Fingerprinting" Redivivus. Fisher, W.P. Jr. Rasch Measurement Transactions, 2001, 14:4 p.785
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