78 



TECHNICAL BULLETIN 7 



tensity for the entire pullet laying year. It should furnish a reasonalily true 

 measure of the bird's ability to lay throughout the year. Since the relation 

 of broodiness to annual rate has already been considered, it seems advisable 

 to correlate annual rate witli annual yield. The calculations gave the follow- 

 ing constants: 



Number of birds .... 

 Mean annual rate .... 

 Anniuil rate standard deviation . 

 Mean annual egg yield . 

 Annual egg yield standard deviation 

 Coefficient of correlation 



2289 



.56.38 



±9.86 



172.21 



±46.61 



-|-.6ri7 ± .0077 



A very sensible positive correlation was found l)etween annual rate and 

 annual egg yield. Annual rate is thus a very dependal)le measure of a bird's 

 ability to lay during her pullet year. 



39. Correlation Befiveen Times Brooihj and Annual Production — Pullet Year. 



Tlie records of 2215 birds broody and non-broody are tabulated and the 

 coefficient of correlation calculated between times broody and annual produc- 

 tion. Constants arrived at follow: — 



Number of birds .... 



Mean times broody 



Times broody standard deviation . 



Mean annual production 



Annual production standard deviation 



Coefficient of correlation 



224.5 



1.44 



±1.98 



173.06 



±46.40 



—.2126 



.0136 



This constant is false because the table is made up of two genetically dis- 

 tinct races, namely, broody and non-broody. 



Table 2. — Relation of Broodiness to Egg Record. 

 Times Broody Number of Birds Egg Record 





 1 

 2 

 3 



■ 4 

 5 

 6 

 7 

 8 

 9 



10 

 11 

 12 

 13 



1121 



312 



259 



220 



149 



72 



47 



28 



17 



9 



5 



2 



1 



1 



181.31 

 178.32 

 156.62 

 156.50 

 158.65 

 162.58 

 1.53.59 

 140.14 

 1.55.50 

 147.72 

 145..50 

 160.50 

 1.55.50 

 145.50 



Reference to table 2 above shows that the 1121 non-broody birds averaged 

 181 31 eggs per year. Close to tiiis group in production is the class of 312 

 birds with but one broody period, averaging 178.32 eggs. A somewhat gradu- 

 al but not regular decline begins with the group broody twice. No further 



