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 
THREE 
AVERAGE 
DEVIATION 
AVERAGE 
DEVIATION 
SQUARE ROOT OP MEAN 
MONTHS 
WITH REGARD TO SIGN 
WITHOUT REGARD TO SIGN 
SQUARE DEVIATION 
USED AS BASE 
Actual 
Percentage 
Actual 
Percentage 
Actual 
Percentage 
OF PREDICTION 
deviation 
deviation 
deviation 
deviation 
deviation 
deviation 
Nov.-Jan. 
+ 2.09 
1.33 
25.93 
16.45 
33.84 
21.47 
Dec.-Feb. 
+ 0.78 
0.49 
25.31 
16.06 
32.65 
20.72 
Jan.-Mar. 
+ 0.49 
0.31 
25.29 
16.05 
31.58 
20.04 
Feb. -Apr. 
— 4.07 
2.58 
24.16 
15.33 
29.77 
18.89 
Mar-May 
— 0.73 
0.46 
25.42 
16.13 
31.14 
19.76 
Apr -June 
— 2.31 
1.47 
24.33 
15.44 
30.59 
19.41 
May-July 
— 2.12 
1.35 
24.20 
15.36 
29.40 
18.65 
June-Aug. 
— 5.35 
3.39 
23.49 
14.90 
29.80 
18.91 
July-Sept. 
— 0.20 
0.13 
21.36 
13.55 
28.10 
17.83 
Aug.-Oct. 
+ 3.91 
2.48 
21.59 
13.70 
29.23 
18.55 
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. 
