80 TECHNICAL BULLETIN 7 



S2. Correlation Betweeii Total Days Broody and Annual Eyy Yield for 

 Broody Birds Alone — Pullet Year. 



A tabulation made of the ir22 broody I)irds 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 broody ...... 42.87 



Days broody standard deviation .... ±26.84 



Mean annual production ..... 164.89 



Annual i>roduction standard deviation . . ±45.03 



Coefficient of correlation — .1964 ± .0194 



Regression days broody on production . . . — .1171 



Regression production on days In'oody . . . — .329.'5 



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 anniuil egg yield, in section 30. On the wliole, broodiness 

 has been shown to lie negatively correlated with annua! production to a rather 

 moderate degree over the eight-year jicriod co\ered in tliis rejiort. 



3S. Correlation Between the Presence of Broodine.'-s and Annnal Production 

 above the Mean of Broodies and Non-hroodies Comtiined — Pullet Year (Flocks 

 1916-1923). 



The true correlation between the presence of broodiness and high annual 

 egg production is determined below. 



Annual Production Broodv I Non-Broody 



Number al)o\e population mean | 514 . J 665 



Number below population mean I 608 458 



I 



Totals 



1122 I 1123 



Coefficient of correlation — .2640 ± .0132 



The aliove constant is statistically significant and is of sufficient magnitude 

 to ',varrant the assumption that broodiness is negatively correlated with higli 

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

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

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

 eliminating liroodiness, yet tlie mean annual Qs:g records of the flocks have 

 been stable since 1920. Very likely broodiness has played a gre;!ter ]Kirt in 

 affecting production in some years tium on otliers. Tlie two following sec- 

 tions show that the correlation between l)roodinesS and annual record has not 

 been intimate either in 1916 or 1923. 



