218 GENETICS: J. A. HARRIS ET AL. PROC. N. A. S. 



error of prediction was determined for each of these groups, and these 

 averages represent the upper and lower limits of the shaded areas. The 

 upper limit represents, therefore, the average deviation (for the period for 

 which prediction is made) of all birds which make a higher record than that 

 predicted for their class. The lower limit of the shaded area marks the 

 average deviation for all birds which show an egg record lower than that 

 predicted. These diagrams, which are quite typical of the whole series, 

 certainly indicate excellent prediction. 



The results for the combined records of three consecutive months are 

 shown in table 2. These show that greater accuracy of prediction 

 may be obtained when the records of three months are used as a basis of 

 prediction. Such a result is to be expected on a priori grounds. A care 

 ful comparison of the constants in tables 1 and 2 will show, however, that 

 the improvement resulting from the trebling of the number of months used 

 as a basis of prediction is not great. 



TABLE 2 



ERRORS OF PREDICTION OF ANNUAL EGG PRODUCTION FROM THE RECORD 

 OF THREE CONSECUTIVE MONTHS 



Prediction of the number of eggs which will be laid in the period subse 

 quent to the month or group of months used as a basis of prediction may 

 also be made. The errors for such a series of predictions, in which each 

 individual month of the year (with the exception of the final month) has 

 served as a basis for the prediction of the egg production of the remaining 

 months of the year, are shown in table 3. The constants in this table 

 show that when the period for which prediction is made is a long one a de 

 gree of accuracy fairly comparable with that for the whole year is attain 

 able. The absolute values of the average deviation without regard to 

 sign and of the square root of mean square deviation necessarily become 

 smaller as the period for which prediction is made becomes shorter. The 

 relative (percentage) error, however, increases. Thus the accuracy of pre 

 diction decreases rapidly as the period for which prediction is made be 

 comes shorter. 



