6 MASS. EXPERIMENT STATION BULLETIN 416 



The winter egg records of the birds were high, as shown by the mean of 91 eggs, 

 but the variability was great amounting to more than 27 percent. Regression of 

 winter egg weight on winter egg production was not linear so that the correlation 

 ratio .1915 expresses the association. While the association was not intimate, it 

 is significant and shows that egg size up to January first does decline as egg pro- 

 duction increases. 



7. Winter Production and March Egg Weight 



Possible association between winter egg production and egg weight during the 

 month of March is important.' Records are available on 612 pullets whose eggs 

 were weighed in March. The following constants were derived: 



Number of birds 612 



Mean winter production — eggs 96.97 



Winter production standard deviation . . + 26.85 



Mean March egg weight — grams 60.54 



Egg weight standard deviation + 3.95 



Coefificient of correlation - .0997 + .0270 



The correlation shown above is low but probably significant. It seems reason- 

 able to assume, therefore, that egg weight during March, the popular month for 

 hatching, is not greatly affected by the number of eggs laid up to March 1. 



8. Winter Production and Annual Egg Weight 



It is desirable to know whether there is a correlation between winter egg pro- 

 duction and annual egg weight. Records are available on 430 females from which 

 the following constants were calculated: 



Number of birds 430 



Mean winter production — eggs 98.10 



W'inter production standard deviation ... ± 27.89 



Mean annual egg weight — grams 58.51 



Egg weight standard deviation + 3.79 



Coefificient of correlation + .0004 ± .0325 



The mean annual egg weight was 58.51 grams, which is equivalent to 24.8 

 ounces to the dozen. The population studied evidently carried an inheritance 

 for large egg size along with a relatively low degree of variabilit\'. Regression 

 was linear but there was no correlation between winter egg production and 

 annual egg weight in the population studied. 



9. Annual Production and Annual Egg Weight 



Investigators are not in agreement concerning the relation between annual 

 production and mean annual egg weight. Atwood (1928), after rather extensive 

 studies with White Leghorns, concludes that there is no relation between the 

 number of eggs laid and the average size of the eggs. Marble (1930, 1931) made 

 extensive studies on factors affecting egg weight in White Leghorns, Barred 

 Plymouth Rocks, and Rhode Island Reds. He showed that the regression of egg 

 weight on number of eggs was non-linear. By using the correlation ratio he 

 found a significant negative correlation between number and weight of eggs in 

 White Leghorns but not in Barred Plymouth Rocks or Rhode Island Reds. 



