200 



TECHNICAL. BULLETIN 9 



13. Correlation Betiveen Whiter Production ami Annual Persistency. 



Winter production during the pullet year is represented by the number of 

 eggs laid from first egg to tiie end of Feiiruary. It has already been pointed 

 out by many workers as a valuable criterion of annual production. Class 

 intervals of ten have been used to make the correlation table for the 2151 

 birds with winter records. Constants computed follow: 



Numl)er of birds ....... 2151 



Mean winter production ...... 62.49 



Winter production standard deviation . . . ±25.44 



Mean annual persistency 302.82 



Persistency standard de\iation .... ±59.32 



Coetficient of correlation . .... -)-.4551±.011.? 



Regression ]iroduction on i)ersistency . . . -|-.195 



Regression persistency on ]iroduction . . . -|-1.061 



The degree of correlation between winter production and annual persistency 

 is positive and of appreciable magnitude. Selection for persistency based on 

 winter records should be of considerable value. Such a condition might be 

 anticipated in view of the high correlation l)etween early maturity and winter 

 production and between early maturity and persistency. 



14. Correlation Betrveen Winter Production Greater Than the Mean and 

 hijih Periti^stency. 



In tlie tabulation below the population is classified into four qualitative 

 groups, namely, high winter producers, low winter producers, possible genet- 

 ically highly persistent, and possible genetically low persistent. The correla- 

 tion is then determined between production above the mean and high per- 

 sistcncv. 



Coefficient of correlation +.5306±.0104 



This coefficient of correlation demonstrates a positive relation between high 

 winter egg record and high persistency. In other words, selection based on 

 winter records greater than the average should increase the percentage of 

 late-molting or persistent birds. 



