80 'lECHXICAI. BULLETIN 7 



32. Correlation Jietween Total Days Broodi/ and Annual Egg Yield for 

 Broody Birds Alone — Piillet Year. 



A tabulation made of the 1122 broody birds gives the true correlation be- 

 tween degree of i)roodiness and pullet-year production. Constants obtained 

 are the following: — 



Number of birds ....... 1122 



Mean days brood}- 42.87 



Days broody standard deviation .... ±; 26.84 



Mean annual production ..... 164.89 



Annual production standard deviation . . ±45.03 



Coefficient of correlation — .1964 ±: .0194 



Regression days broody on production . . . — .1171 



Regression production on days broody . . . — .3295 



Tlie degree of correlation between total days broody and annual egg record 

 is not at all intimate. It is in very close agreement with the constant for 

 times broody and annual egg yield, in section 30. On the whole, liroodiness 

 has been shown to be negatively correlated with annual production to a rather 

 moderate degree over the eight-year })eriod covered in this report. 



■3-3. Correlation Betzveen the Presence of Broodinei^s and Annual Production 

 above the Mean of Broodies and Non-broodies Combined — Pullet Year (Flocks 



lOin-1923). 



Tlie true correlation between the presence of broodiness and high annua! 

 egg ])rodurtion is determined below. 



Coefficient of correlation — .2640 ± .0132 



The above constant is statistically significant and is of sufficient magnitude 

 to warrant the assumption that broodiness is negatively correlated with high 

 annual production. The fact that annual egg record depends upon a vast 

 array of genetic and non-genetic factors should not be overlooked. During 

 the eight-year period being considered there has been constant progress in 

 eliminating broodiness, yet the mean annual egg records of the flocks have 

 been stable since 1920. Very likely broodiness has played a greater part in 

 affecting production in some years than on others. The two following sec- 

 tions show that the correlation between broodiness and annual record has not 

 been intimate either in 1916 or 1923. 



