MASS. EXPERIMENT STATION BULLETIN No. 289 



T.\BLE 2 — H.VTCHING D.\TE IN RELATION TO ANNUAL PRODUCTION. 

 (Lines A, B, and C combined.) 



Coefficients of Variation of Means — Per Cent 



6.06 -I- .50 



4.05-I-.18 



10.70 -I- .97 



8.94 -I- .64 



The coefficients of variation in mean production due to differences in hatch- 

 ing date are recorded at the end of Table 2. These, together with the gross data 

 presented in the table, show clearly that hatching date does affect annual pro- 

 duction and variability in production. Hatching date also appears to have had 

 a greater effect upon variation in the last two generations. The data indicate 

 that about 7 per cent of the variation in annual records may be assigned to dif- 

 ferences in hatching date. 



Change in Body Weight During the Laying Year 



All birds were weighed approximately 365 days after the mean date of first 

 egg to discover how body weight behaves near the close of the laying year. The 

 total population consisted of 149 individuals that showed a weight increase after 

 the first pullet egg, 54 individuals that showed a loss of weight, and 2 individuals 

 having no weight change. The mean annual egg record of the gaining group was 

 225.98. The mean production of the group losing weight was 211.28. Table 3 

 gives the detailed data. 



The coefficient of variation for the twelve mean production records in the 

 gaining group is 9.86±.39 per cent. The coefficient for the losing group is 

 11.09±.72 per cent. The difference is 1.23±.82 per cent. This difference is not 

 statistically significant and indicates that the variation in annual production is 

 independent of gain or loss in weight during the laying year. The data show that 

 body weight change is not a factor aft'ecting variability of annual egg records. 



