On Various Conceptions of Correlation

Introduction. The theory of correlation was first developed on definite assumptions as to the form of the destribution of frequency, the so-called normal distribution being assumed. It seems that Sir Francis Galton was the first to deal with correlation among direct observations. Het developed the practical method, determining his coefficient-Galton's function-graphically. Bravais+ introduced a product-sum, but not a single symbol for a coefficient of correlation. Edgeworth? developed the theoretical side further on the assumption of a normal distribution. Pearson|| introduced the product-sum formula on the assumption of a normal distribution. Yule? developed the regression method of approaching correlation. In the problem of correlation, we wish to find some measure of agreement or disagreement between two sets of paired characters. Under the term correlation two very different meanings have frequently been considered, connection and concordance. Gini** established a distinction between the different meanings of connection and concordance. His researches deal with