TIME TO STANDARD EGG WEIGHT 7 



is almost identical in this group of 297 birds with the mean for the entire 383 

 birds previously considered. 



No simple correlation exists between persistency and time to standard egg 

 weight, and the regression is strictly linear. 



A calculation of the net correlation between annual persistency and time to 

 standard egg weight gives a constant of —.6241 which is highly significant. This 

 constant indicates that about 39 per cent of the variation in time to standard 

 egg weight is attributable to differences in persistency. This relation is largely 

 obscured by the linkage relations between early sexual maturity and high persis- 

 tency pointed out by Hays (1927). 



Correlation Between Winter Egg Production and Time to Standard Egg Weight 



Winter egg production includes all eggs laid from the first pullet egg in the 

 fall or winter to March 1. The entire population of 383 birds was used to cal- 

 culate the simple correlation between winter egg production and time to standard 

 egg weight. The constants determined are as follows: 



Number of birds 383 



Mean winter production, eggs 100.71 



Winter production standard deviation ±22.55 



Mean time to standard egg weight, days 106.93 



Time to standard egg weight standard deviation ±48.33 



Coefficient of correlation +.2599 ±.0321 



Correlation ratio .3373 



A mean winter production of slightly over 100 eggs shows that the birds studied 

 were very heavy winter layers. There is a variability of about 22 per cent which 

 is rather high. 



The regression of time required on winter production is not strictly linear so 

 that the correlation ratio of .3373 really measures the association. Its value 

 squared shows that about 11 per cent of the variation in time required is due 

 to variation in winter production and that heavy winter layers tend to require 

 a longer time interval to attain standard egg size. 



Correlation Between Annual Production and Time to Standard Egg Weight 



Egg size has been shown by a number of workers to be essentially independent 

 of the number of eggs laid in a year. It is important to learn whether annual 

 production affects the time interval to standard egg weight. Annual production 

 used in this report represents the number of eggs laid by each individual in 365 

 days beginning with the first pullet egg. The correlation coefficient was calculated 

 with the following constants: 



Number of birds 297 



Mean annual production, eggs 221.12 



Annual production standard deviation ±37.87 



Mean time to standard egg weight, days 107.34 



Time to standard egg weight standard deviation ±48.21 



Coefficient of correlation +.0429 ± .0391 



Correlation ratio .3015 



Annual egg production was rather high in the population studied, and the 



