The significance of the correlation coefficient when applied to Mendelian distributions / by John Brownlee.

  • Brownlee, John, 1868-1927.
Date:
1910
Catalogue details

Licence: In copyright

Credit: The significance of the correlation coefficient when applied to Mendelian distributions / by John Brownlee. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    Affain the mating is unusual. The table of sires and dams for an o o offspring of colts is as follows :— Sires. Dams. Red. Roan. White. Red 197 (217) 277 (276) 45 (27) Roan . 221 (210) 271 (268) 12 (26) White . 34 (26) 28 (33) 0(3) Alongside the actual figures are placed within brackets those required by random mating. It is seen at once that red matings with white or dominant with recessive are much more numerous than required by chance, a further cause of low correlation (par. 17). The values of the coefficient may now be considered. By the product method r — 'SQS. By the fourfold table when normality is assumed r = -46. If, however, the parentage is taken first, the expected Mendelian population of offspring calculated and the correlation evaluated, we find the aberrance of type among the offspring (the absence of sufficient whites) has lowered the correlation to some extent. A typical offspring for the parentage gives r = -383. Professor Pearson by the contingency method gets r — -40, not greatly in excess of ‘363, and piobably arrived at because he has made the calculation with the red group divided into three classes, and with this increase of division the contingency may be expected to give higher figures. In using the contingency method it is clearly not legitimate to break up one class without breaking up others, especially if one class, as seems here, is arbitrarily divided. One point remains to be considered: What is the correlation between parent and offspring among the different divisions of the dominants, as these, though of the same strain, have considerable variation of colour ? The table for sires and colts is as follows:— Sires. Colts. Red. Red with little White. Red and Wrhite. Red .... 95 27 13 Red with little White. 14 6 6 Red and White . 8 4 11