200 



TECHNICAL BULLETIN f) 



13. Correlation Beticeen Winter I'rodnctioii oikI .liinnni J'ersi.s-tcnci/. 



Winter production diiriiifi' tlie jiullet year is represented by tlie nuiuher of 

 eggs laid from first egg to the end of Fchruary. It lias already lieen pointed 

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

 intervals of ten lia\e been used to make tlie correlation taiile for the 21.51 

 birds with winter records. Constants computed follow: 



Number of birds ....... 21.51 



Mean winter production ...... 62.19 



Winter production standard deviation . . ±2.5.M 



Mean annual persistency ...... 302.82 



Persistency standard deviation .... ±59.32 



Coefficient of correlation . .... -{-.1.5.51iii.011.5 



Regression production on persistency . . . 4-. 19.5 



Regression persistency on ])roduction . . . -|-1.0()1 



The degree of correlation between winter production and annual jiersistency 

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

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

 anticipated in view of the high correlation between early maturity and winter 

 production and between early maturity and jH-rsiskncy. 



14. Correlation Between Winter Production (Irealer Tlxtn the jMean and 

 h i(/ h Pe rsis t en cij . 



In the tabulation below the population is classified into four qualitative 

 groups, namely, high winter produ.cers, low winter producers, possible genet- 

 ically highly persistent, and possible aeiielically low persi.stent. The correla- 

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

 sistencv. 



Below population mean | +24 | 670 



Totals ! 1136 I 101.5 



Coefficient of correlation +.5306±.01O4 



This coefficient of correlation demonstrates a jjositive 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. 



