ANNUAL MOLT AND EGG PRODUCTION 81 



The mean length of the molt period was 65.23 days for the birds showing 

 a weight increase, as compared with 72.17 days for the birds having no 

 change in weight or loss of weight. 



A mean weight increase of 0.67 pound was observed, but the standard devi- 

 ation for weight increase indicates wide variability. The actual range for 

 weight increase was from 0.01 pound to 2.00 pounds. 



The coefficient of correlation between weight increase and lengtli of molt 

 period was — .1220 rt .0424-. This constant is of insufficient magnitude to be 

 of value. 



The correlation ratio of length of molt period to gain in body weight was 

 almost twice as large as th?correlation coefficient. By Blakeman's test, how- 

 ever, the difference in the two constants was equal to only 2.37 times its 

 probable error. This fact suggests that the relationship of the two charact- 

 teristics being considered was not far from linear. 



The regression of length of molt upon weight increase, when tested by the 

 X- method, gave a probability of .2125 of being a straight line. In view of 

 these facts, the correlation coefficient measures the relationship, which ap- 

 pears to be insignificant. 



9. Previoiis Production versus Length of Molt Period. 



Previous-production records include all eggs laid from the first pullet egg 

 up to the non-productive period associated with complete molt. The length 

 of time concerned varied from less than 12 months to as high as 14 or 15 

 months in some cases. Such production records represent a long period of 

 intensive physiological activity in heavy laying birds and the intensity of this 

 activity may affect the duration of molt. 



A population of 929 birds was used in this study. Both production and 

 duration of molt were divided into class intervals of 10. The following cons- 

 tants were derived from the correlation table: 



Number of birds _ - 929 



Mean length of molt period — days 75.60 



Molt period standard deviation — days. ±30.38 



Mean previous production — eggs ._ 231.19 



Previous production standard deviation — eggs ±41.30 



Coefficient of correlation...... —.3105 ± .0200 



Correlation ratio — .3695 



The mean previous production of all birds before molting was 231.19 

 eggs. The variability in production as measured by the standard deviation 

 was rather wide, with a range extending from 71 to 350 eggs. This varia- 

 bility was no doubt enhanced by lengthening the production period beyond 

 a full year. 



The correlation ratio of molt duration to previous production was of 

 molt period amounted to ^.3105 ± .0200 and is considered significant. This 

 constant squared (.0964) indicates, according to Ezekiel (1929), that 9,64 

 per cent of the variability in duration of molt may be attributed to previous 

 production. 



The correlation ratio of molt duration to previous production was of 

 somewhat greater magnitude than the correlation coefficient. By Blakeman's 

 test the difference between the two constants was equal to 4.72 times its 



