Caste and Race in India c9.14

c9.14

When we compare two groups, what we want to know is not merely the differences between the two groups as regards the cephalic index or nasal index separately, but we want an expression which conveniently sums up all the differences in the various attributes that we may like to compare. Such an expression was used by Mr. T. A. Joyce in 1912. In order to compare two groups he starts with one character, say, the cephalic index, and works out the fraction (M₁ - M₂)/(√(σ₁² + σ₂²)) where M₁ and M₂ are the means for the cephalic indices of the two groups, M₁ - M₂ is their difference without regard to sign, and σ₁, σ₂ are the standard deviations. Similar fractions are found for as many characters as one likes, and all of them are added together. This sum is called the "Differential Index".³ The expression is a convenient quantity showing the actual differentiation of two peoples and can be fruitfully used for comparisons. Another great advantage of this expression is that by its help we can include for comparison absolutes like the cephalic length, which have, unfortunately, been too much neglected in anthropological work. Further this item is of special importance in the field of Indian ethnology; for here we have sometimes to deal with two dolichocephalic peoples whose absolute measurements of the head are essentially different. Thus the Chamar of the United Provinces has a cephalic index of 72·90, while his cephalic length and cephalic breadth are 185·18 and 134·9 respectively. The corresponding figures for the Chhatri of the same province are: 78·12, 188·35, 137·68. We have given in the appendix the differential indices for selected castes. In this chapter we have attempted to attack the problem of caste with the help of this index.