174 A BIOMETRIC STUDY OF BASAL METABOLISM IN MAN. 



series emphasizes the fact that even series comprising over 60 individ- 

 uals each are not large enough to give wholly accurate mean predictions 

 of metabolism. Metabolism constants are highly variable, and this 

 has as a necessary consequence a high probable error of a mean constant 

 based on a number of individuals which to the experimental physiol- 

 ogist would seem to be very large. The reader will of course note that 

 since the average deviations of predicted values differ in sign in these 

 two series, the result of combining the two series for the purpose of 

 predicting standard control values, as we shall do later in this volume, 

 will be an average deviation much more nearly the theoretical zero in 

 amount. How close to the theoretical the average of values predicted 

 from these combined series will lie can, of course, be determined only 

 in the future when the necessary experimental data have been collected. 



TABLE 66. Average deviation with regard to sign of total heat-production as predicted by 

 linear equations from the actual heat-production. 



Comparable results, as far as the opposite signs are concerned, are 

 found in the two feminine series. The magnitudes of the deviations 

 are, however, much greater. We find, in fact, averages ranging from 

 about 50 to about 80 calories, instead of from 2.5 to 9.6 calories, as 

 in the general male series. Expressed in percentages of the mean, 

 the deviations are of the order 3.8 to 5.9 per cent, instead of generally 

 lower than 1 per cent. The conclusion to be drawn from this result 

 is obvious. Prediction of the metabolism of women can not be carried 

 out by these equations with the degree of certainty that is possible in 

 dealing with men. To what extent this may be due to the smaller 

 number of records of women as yet available, and to what extent it 

 may be looked upon as due to age heterogeneity or as indicating real 

 biological differences between the sexes, must remain a problem for 

 further investigation and consideration. 



