VOL. 7, 1921 GENETICS: J. A. HARRIS ET AL. 215 



the unknown, we have calculated equations based upon the data of the 

 International Egg Laying Contest at Storrs, Conn., during the six contest 

 years, 1911-1917, inclusive. We have then used these equations to pre 

 dict the annual production (and the production of groups of months) for 

 the birds of the 1917- 18 contest, using as a basis of prediction the individ 

 ual months of the laying year separately, pairs of successive months and 

 groups of three months. Our conclusions concerning the value of the 

 equations depend, therefore, not upon a priori considerations but upon the 

 results of actual tests of accuracy of prediction for series which were un 

 known as far as the determination of the constants of the equations is 

 Concerned. 



Consider first of all the results of the attempts to predict the annual 

 egg production of 415 White Leghorn birds observed at Storrs from Nov. 

 1, 1917 to Oct. 31, 1918 from the records of a single month s production. 



The results of the three criteria of accuracy of prediction are summa 

 rized in table 1. 



TABLE i 



ERRORS OF PREDICTION OF ANNUAL EGG PRODUCTION FROM THE RECORDS 

 OF INDIVIDUAL MONTHS 



Considering first of all the absolute values we note that the average 

 errors with regard to sign are generally low. Thus the prediction from No 

 vember and from January production gives on the average 3 eggs too many 

 ior the year. For December, February, March and August the predic 

 tion is in error by less than 2 eggs. The values predicted from April, May, 

 June, July, September and October records are from 4 to 7 eggs in error. 



The average deviations without regard to sign are of course much larger 

 nnce they constitute a measure of the error of prediction of the records of 

 ndividual birds. They range from 24.8 to 30.1 eggs. The significance 

 }f errors of this magnitude will be more clearly brought out later. 



The square root of mean square deviation also shows considerable regu- 



