.38 TECHNICAL Bl'LLETIX 7 



in this manner to measure directly the effect of hroodiness on fecundity. This 

 intense broody strain differs from the foundation birds more in the distribu- 

 tion of broody periods throughout the laying year tlian in the ninnl)cr of 

 broody periods. 



Complete records of hroodiness are also maintained on every female of tlie 

 experimental flock to augment data collected in the broody experiment. 



ExD TO Be Attained 

 A flock of poultry breeding true for hroodiness and non-broodiness. 



Scope of This Report. 



In this bulletin consideration is given to the actual relationship lietwecn 

 pullet-year egg production and the broody trait as manifested during tiie fir.st 

 laying year. Coefficients of correlation have been calculated as follows: 



Between hroodiness and rate. 



December rate — Sections 1, 2, 3, 4, 5, Iti, 17. 

 Winter rate— Sections 6, 7, 8, 9, 10, 18, 19. 

 Annual rate— Sections 11, 12, 13, 14, 1.5, 20, 21. 



Between times broody and length of broody periods. 

 Section 22. 



Between winter rate and annual rate. 

 Section 23. 



Between winter rate and annual eyy yield. 

 Section 27. 



Between annual rate and ^annual eya yield. 

 Section 28. 



Between hroodiness and eyy yield. 



Winter production — Sections 24, 25, 26. 



Annual production— Sections 29, 30, 31, 32, 33, 34, 3.5. 



COEFFICIEXT OF CoRREI.ATIOX. 



The coefficient of correlation furnishes a concrete measure of the tendency 

 of two characteristics to nio\e together, to move in opposite directions, or to 

 behave independently. In tliis particular study the characteristics studied 

 both belong to the same individual fowl. Either a significant positive or 

 negative correlation coefficient is useful to the breeder as a guide, and the 

 itiagnitude of the coefficient shows him the relative amount of dependence 

 l)etween the traits or characters considered. The value of a coefficient of 

 correlation from the biological standpoint depends upon its ai)Solute magni- 

 tude and upon its relation to its probable error. A coefficient at least tliree 

 times as great as its probable error is generally considered significant, e\en 

 though its absolute magnitude is small. The deductions reported in this 

 bulletin are based on the al)Ove conception. King (1923), however, states 

 that the correlation coefficient should lie more tiian six times its proliable 

 error. He further states that a correlation coefficient of less than .30 indicates 

 a lack of marked correlation, that over .50 shows decided correlation. Further- 

 more, the correlation coefficient with its regression coefficients may be used 

 for jnirposes of prediction. The value of a knowledge of the degree of correla- 



