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



larity from month to month. These measures are naturally considerably 

 larger than the average deviation without regard to sign. They range 

 from 32.9 to 38.8 eggs. 



It is clear that the annual egg production of birds similar in origin to the 

 series upon which the prediction equations were based and maintained un 

 der similar conditions may be predicted with a relatively high degree of 

 accuracy providing their record for any month is definitely known. 



The order of the errors will be more readily understood by expressing 

 them in relation to the average production of the flock, as shown by the 

 percentage deviations. 



We note that in predicting from December, February and August records 

 the average error with regard to sign is less than one per cent of the average 

 annual yield of the flock. In predicting from November, January and 

 March the error lies between one and two per cent. When April, May, 

 June, July, September and October records are used as a basis of predic 

 tion the average errors of prediction are from 2.50 to 4.50 per cent of the 

 average annual yield. 



The average deviations without regard to sign are less than 20 per cent 

 of the annual production. The values for the individual months range 

 from 15.7 for September to 19.1 for January. 



The square root of mean square deviation is less than 25 per cent of 

 the average annual production. The individual values range from 20.9 

 for September to 24.6 for January. 



These two latter tests may at first seem to indicate very unsatisfactory 

 prediction. Such is not, however, the case. These give the average 

 errors either above or below the true record made in the prediction of the results 

 for an individual bird. The thing which is required in practise is generally 

 the prediction for a group of birds of a particular grade of egg record for the 

 month used as a base of prediction. In a flock of 415 birds this has been 

 shown to be possibe with an error of less than 5 per cent of the annual produc 

 tion when prediction is made from the record of any month of the year; 

 and with an error of less than I per cent when prediction is based upon the re 

 cords of a number of the individual months. 



Lack of space precludes a discussion of the results of the prediction of 

 the annual record of the bird from the combined record of two consecutive 

 months. We may, however, illustrate the accuracy of prediction from the 

 combined record of two consecutive months by means of the figures in dia 

 gram 1 which shows the accuracy of prediction from November plus Dec 

 ember and from April plus May in comparison with the results of predic 

 tion from November and April. In these the estimated production is slit &amp;gt;\vn 

 by a straight line. 



The actual production for the year for which prediction is made is shown 

 by solid dots for each group of birds as classified by monthly or bimonthly 



