PREDICTING EGG PRODUCTION IN WHITE LEGHORNS 301 



uction are shown in diagram 10. In both cases the upper figure represents 

 he prediction of annual production. The lower figure shows the prediction 

 f the groups of remaining months and will be discussed in a subsequent 

 sction. 



After the discussion of the preceding diagrams these graphs are self- 

 xplanatory. 



When these results are compared, as in the last two columns of the tables, 

 ith those for prediction from a single one of the three months the differ- 

 nces are surprisingly small. For example the most important test, that 

 f the average deviation with regard to sign, shows that 11 of the 30 

 inferences are less than 1 egg per year; 3 are less than 2 eggs per year; 

 r hile 16 are 2 eggs or more per year. In no case is the difference as much 

 s 7 eggs per year. The difference in percentage deviation is in no case 

 s large as 4 percent. 



Turning to the comparison of average deviation without regard to sign 

 r hen prediction is made from trimonthly periods and from the records 

 f individual months we note that the differences are without exception 

 ositive in sign. Thus they show a greater error when prediction is made 

 rom a single monthly record. The differences are, however, always less 

 lan 7 eggs per year and are generally less than 5 eggs. The percentage 

 ifferences vary from 1.3 to 4.4 percent when both percentages are based 

 n the annual total. 



Similar results are obtained for the square root of mean square deviation, 

 he deviations are larger throughout when prediction is made from single- 

 ion ths records than when made from three-months records. The differ- 

 nces are not, however, large. They range from 2.05 to 7.79 eggs, or from 

 .30 to 4.94 percent of the annual average production. 



Thus while practically without exception a closer prediction of the 

 nnual egg record of individual birds can be made from three-months 

 reduction the difference between a three-month period and a single- 

 lonth period is by no means so large as one unacquainted with statistical 

 icory might have assumed. 



ENETTCS 6: My 1921 



