PREDICTING EGG PRODUCTION IN WHITE LEGHORNS 307 



rrors than prediction from the combined record of three months. The 

 dfferences are, however, insignificant, varying from 0.02 to 1.68 eggs. It 

 5 clear, therefore, that if the linear equation be used for the purpose of 

 predicting the yield of a group of remaining months, about as good results 

 br practical purposes may be obtained from single month records as from 

 he sum of three months records. 



It is quite possible that with equations other than the linear this will 

 iot be the case. Such equations will be investigated in future work. 



Comparison of the two- and three-month periods as bases for the prediction of 

 the egg record of the subsequent months 



In the foregoing discussion comparisons between the value of single- 

 ionth periods and two-month periods and between single-month and three- 

 lonth periods as base s for prediction have been made. It will be of some 

 aterest to compare two- and three-month periods in the same way. Cer- 

 ain of the data may be rearranged from preceding tables. Special calcu- 

 itions would, however, be necessary to complete all of the possible com- 

 arisons. It is evident that for a critical comparison between the two 

 roups it is necessary to deal with the egg record of a group of remaining 

 months. Thus in comparing November-to-january production with 

 s T ovember-and-December or December-and- January production as bases 

 f prediction it is necessary to determine the accuracy with which the egg 

 reduction of February to October may be predicted since none of the 

 lonths included in the base of prediction should also occur in the period 

 pr which prediction is made. 



Limiting our attention to the comparisons which can be made from the 

 .ata in the preceding tables 7 we note that in some cases there is a larger 

 verage deviation with regard to sign in predicting from two-months and 

 i some cases a larger error in predicting from three-months production. 



The same may be shown to be true for the average deviation without 

 egard to sign and for the square root of mean square deviation of the 

 predicted from the actual values. Thus there is little practical advantage 

 i dealing with three-months production as compared with two-months 

 reduction as bases for the prediction of the record of a group of subsequent 

 lonths. 



7 The subsidiary tables upon which the following conclusions were based may be formed from 

 ibles 5 to 7 and 11 to 13. It seems unnecessary to publish these tables here. 



ENETICS b: My 1921 



