February, 1921. 



SCIENTIFIC AGRICULTURE. 



65 



between pehac bones. TMs expression correlated to evidence all points to the conclusion that this 



egg production is shown in table 5. T^iere is a deci- "system" is not a satisfactory method of. predicting 



dedly significant correlation but when compared with a bird'.s production. 



the other coefficients of correlation in table 5, there For the present experiment, abdominal measure- 

 is no advantage in working this out for use in selecting ments were changed to a "finger" classification on 

 birds for production, as the original measurements the following ba-sLs: 1-2.9 cm = 1 finger; 2.9-4.5 em 

 give a higher correlation than the expression in which = 2 finger; 4.5-6 em = 3 finger; "over 6 em ^ 

 they are combined. 4 fingers. Condition of birds as heretofore considered 



THE HOGAX "SYSTEM". — The Hogan "sj-s- was used for the following: Hogan classification, 2 = 



tem" is intended primarily to serve as a means of 1 (Hogan); 3 = 2; 4 and 5 = 3. When no allow- 



prcdicting the egg production of a hen or a pullet, anee was made for condition, the coefficient of cor- 



In the present experiment, it was, of course, impos- relation for expected to actual production was .1481 



sible to use it for this purpose, but the data taken ±.0394. There is a small correlation shown, but less 



could be used to find out whether there was any re- t,han the correlation between abdomen and eg^ pro- 



lation between the expected production as based on duction as shown in table 3. In other words, com- 



this "system" and the actual pa.st production of the bining thickness of pelvis with si^e of abdomen is 



birds. a disadvantage .so far as showing relationship to pro- 



Whitaker (9) reports a trial of this so called "sj-s- duction goes. It is well to note in this connection 



tem" in which ilr. Hogan predicted the number of tJiat combining two measurements, even when both 



eggs that eacA of about one thousand birds would lay are related to egg production, does not seem to give 



at the First All Northwestern Laj-lng Contest. A an expression that is more closely related to produc- 



correlation table was made (by present writer) of tion but rather the reverse. This was pointed out in 



tie predicted and actual production of 48 birds from connection with table 5 and others bear out the same 



the report given and another for the rank of 117 point which would seem to indicate that an expression 



birds for which the actual and predicted rank are giving a closer correlation to production than the 



given. The coefficients of correlation were .0641 ± original measurements is rather hard to find. 

 .09/0 and .01 (9 ±.0624 respectively. The deviations Taking the expected egg production based .strictly 



of predicted production from actual for 681 birds on the instructions given by Hogan (4) with the 



were also tabulated. The.se show tpat for 343 birds actual production as shown by the records gave a 



the de^-iat.ion was less than 50 eggs, while 338 birds coefficient of correlation of .0059 ±.0403. It will be 



gave a deviation of over 50 eggs. For S. C. Wliite seen that t^ere is apparently no relation between the 



Leghorns 161 out of a total of 335 birds showed a two in spite of the fact that there is a correlation, 



deviation of over 50 eggs or the average' deviation though somewhat small, between past production and 



would be very close to 50 eggs. While the number condition of the birds at the time that they were 



of birds used in the correlation tables was small, the measured. An explanation of this result is undoubt- 



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