178 



TECHNICAL BULLETIN 8 



12. Correlation Between Age at First Egg Below the Mean and the Presence 

 of Winter Pause for the Total Population. 



Coefficient of correlation 



+.3578 ± .0101 



Attention should be called to the fact that time of beginning to lay and 

 age at first egg each show almost identical correlation coefficients to the pres- 

 ence of winter pause. The interjjretation is that age at first egg is the chief 

 determinant of time of begmning to lay when the hatching dates are constant 

 from vear to year. 



13. Correlation Between Weight at First Egg and Length of Winter Pause. 



Available for this study are the records of 2106 birds, classed as pause 

 birds, on which the body weight on the day of laying their first egg was 

 secured. Thus a very small nimiher of the 2134 birds previously considered 

 is omitted from this study. The class interval used for body weight was the 

 half pound and the ten-day class interval was again used for winter pause. 

 The following; constants were determined: 



Number of birds 



Mean weiglit at first egg 

 Weiglit at first egg standard deviation 

 Mean length of winter pause 

 Winter pause standard deviation 

 Coefficient of correlation 

 Regression of weight on winter pause 

 Regression of winter pause on weight 



2106 

 5..55 

 ±.72 

 32.32 



±22.01 

 +.0161 

 +.0005 

 +.4908 



:.0147 



A range in body weight from 3.25 to 8.25 lbs. occurs in the population 

 studied. The magnitude of the standard deviation in weight indicates, how- 

 ever, that extremely small or extremely large birds are the exception, since 

 the coefficient of variability for body weight is only about 13 per cent. 



The coefficient of correlation between body weight and winter pause dura- 

 tion is mathematically insignificant. This furnishes rather concrete evidence 

 that a pullet's body weight when she lays her first egg bears no relation to 

 the length of her winter pause. 



