198 



TECHNICAL BULLETIN 9 



Winter pause duration is subject to extreme fluctuations. Its range extends 

 from 4 to 130 days. The magnitude of its standard deviation indicates that 

 its duration is affected by a considerable number of variables. 



The above coefficient of correlation gives a statistically significant yet far 

 from pronouaced correlation between length of winter pause and annual per- 

 sistency. There is but a very slight tendency for long-pause birds to persist 

 longer than do short-pause birds. 



10. Correlation Between Annual Pers'istencij Above the Mean ami the Pres- 

 ence of Winter Pau^e. 



This section is devoted to a consideration of the presence of winter pause 

 and annual persistency above the population mean of 303.20 days. Such a 

 correlation will bring out any possible association between the heritable char- 

 acteristic, winter pause, and high persistency which, in this instance, means 

 persistency greater than the mean of the population studied. The classifica- 

 tion follows: 



Totals 



1348 



801 



Coefficient of correlation 



-.2156±.0139 



The correlation coefficient is significant though of only moderate magnitude. 

 Possibly winter pause birds tend to lay for a slightly longer period than do 

 non-pause birds because the former are more likely to be early-hatched (Hays 

 and Sanborn 1926b), and early-hatched birds tend to be more persistent than 

 late-hatched birds. The exact relation between pause and persistency can 

 only be discovered through the partial coefficient of correlation and will be 

 reported in a later publication. 



11. Correlation Between Total Days Broody and Annual Persistency. 



The heritable trait, broodiness, will next be considered in so far as its in- 

 tensity as measured by total days broody is correlated with persistency. Only 

 the pullets that exhibited broodiness during their first laying year are used 

 to obtain the constants below: 



