62 TECHNICAL BULLETIN 7 



be as valuable for study as one of marked uniformity for all cbaracteristics. 



Some short-time record of production is often made use of liy commercial 

 poultrynien in predicting the laying ability of a pullet for the year. Winter 

 pause is likely to appear in many birds during December and is very pro- 

 nounced in earlier birds. Other birds beginning their laying year early and 

 continuing to lay regularlj' through December, as well as those starting their 

 laying year in December, will as a rule have high December rate. Possibly 

 November records would be freer from the winter pause, but such records 

 would be less valuable than December records for predicting either winter or 

 annual egg records, as Harris and Goodale (1922) have shown. It therefore 

 seems advisable to use December rate in studying the relation of broodiness 

 to rate. 



A total of 194-5 birds consisting of both broody and non-broody are included 

 in the study. The range in times broody is from to 12, divided into 13 

 classes. The range in December rate is from 1 to 100, divided into live-unit 

 classes. Constants calculated from this study follow: 



Number of birds ....... 194.5 



Mean times broody . . . . . 1.41 



Times broody standard deviation . . . ±1.98 



Mean December rate ...... .59.60 



December rate standard deviation . - . ±20.40 



Coefficient of correlation ..... -)-.0639 ± .01.52 



The constants given above impress the reader with the marked variability 

 in the birds studied, both with regard to times broody the first year and 

 December rate of production. The apparently abnormal standard deviation 

 in times broody is due to the large percentage of non-broody birds (.5^.23 

 per cent). In other words, an impure population is concerned. 



The magnitude of the standard deviation in December rate signifies very 

 marked variation in rate of laying for December. E\'en such a short-time 

 measure of fecundity is subject to excessive variability. 



The coefficient of correlation between times broody and December rate, 

 although more than three times as great as its probable error, is of question- 

 able magnitude and is a false correlation as Section 2 shows. 



2. Correlation Between Times Brooily and December Rate for Brood)/ Birds 

 Alone — Pnllet Year. 



In order to measure the relation of degree of broodiness, as indicated by 

 the number of periods, to December intensity, only birds actually going brood}' 

 have been used in the calculation of the correlation coefficient. Of the group 

 of 1945 individuals studied in section 1, 949 birds actually went broody dur- 

 ing the pullet year. This number has been used io study the relation of 

 degree of broodiness to December rate. Constants arrived at follow: 



Number of birds 949 



Mean times broody 2.89 



Times broody standard deviation . . . ±1.95 



Mean December rate 61.24 



December rate standard deviation . . . ±20.11 



Coefficient of correlation -|-.0145 ± .0219 



Regression broodiness on rate .... +.0014 



Rearession rate on broodiness .... -|-.1498 



