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New conversion formulae for light‐skinned populations using Photovolt and E.E.L. Reflectometers
Author(s) -
Lees Francis C.,
Byard Pamela J.,
Relethford John H.
Publication year - 1979
Publication title -
american journal of physical anthropology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.146
H-Index - 119
eISSN - 1096-8644
pISSN - 0002-9483
DOI - 10.1002/ajpa.1330510312
Subject(s) - reflectivity , regression , mathematics , statistics , linear regression , optics , physics
Recent research in Belize revealed that published conversion coefficients for use between the two most commonly used reflectance spectro‐photometers were inadequate when applied to dark‐skinned populations. New research in Ireland shows that the published conversion coefficients for light‐skinned populations are also inadequate. A total of 320 school children from Longford, Ireland were measured for skin reflectances at the upper inner arm site with the Photovolt Model 670 and the E.E.L. Reflectance Spectrophotometers. Six and nine filters respectively were used to sample the visible spectrum. Multiple regression techniques were then used to estimate new conversion coefficients which accurately predict readings for one instrument by using some or all of the measurements from the other. Double cross‐validation techniques showed the inadequacy of the old (1967) formulae and the very high accuracy of the new ones. Some problems encountered in this study, but not in the one which produced new formulae for dark‐skinned populations, suggest further work may be necessary. Additional independently sampled light‐skinned populations have not been measured on both machines, so conclusive cross‐validation of the new coefficients must remain tentative. Despite this drawback, the new formulae presented here are almost certainly an improvement over the old ones. These new conversion formulae may allow previously impossible comparisons of worldwide data on similar populations.