226 



Maine Agricultural Experiment Station. 1918. 



The necessary reduction of the statistics of table 7 to theit 

 means and constants to measure their variability is seen in 

 table 8. 



TABLE 8. 



Means, Standard Deviations and Coefficients of Variation for' 



the Hours between Observed Appearance of Heat and 



Service of the Cow. 



Sex of Offspring 



Discovery of Heat Standard Deviation 

 to Service 



Coefficient of 

 Variation 



Male 



Female 



Two males 



Male and female 



Two females 



Sex unknown 



Total successful services. 

 Unsuccessful services 



5.9550± .1129 

 6.1417± .1165 

 1.9167± .6619 

 4.6667± .9554 

 9.5833±1.2850 

 5.1548± .4426 

 6.0200± .0795 

 5.8627+ .1574 



5.3355±.0798 

 5.42S5±.0824 

 1.6997+.46S0 

 4.906S+.6756 

 3.2998±.9086 

 4.2528+.3130 

 5.3596+.0563 

 6.0009-K1113 



89.5967+ 2.1654 

 88.3882± 2.1467 

 88.6783+39.1673 



105.1450±25.9416 

 34.4333±13.5529 

 82.5020+ 9.3316 

 89.0302± 1.5032 



102.3565± 3.3417 



The above data indicates the following conclusions. 



(1) Successful services may occur 41 hours after the 

 first observance of heat. 



(2) The duration of the observed period of heat before 

 service in the unsuccessful services extends up to 69 hours. 

 The interval hours covered in these unsuccessful services is 

 therefore slightly longer than in the successful ones. 



(3) The average number of hours between observance 

 of heat and services is the same (within the errors of random 

 sampling) for the successful and unsuccessful services. 



(4) When analyzed in groups of five hours periods it is 

 found that the unsuccessful services occur most frequently in 

 the 0-5 and 25 and above hour periods as compared with the 

 successful services. From this the conclusion seems justified 

 that the best time for service would be between 5 and 10 hours 

 after appearance of heat. 



(5) The choice of this time for service would not cause 

 any difference in the sex of the resulting calves for Table 8 

 shows the average number of hours from the time heat is ob- 

 served to service is the same whether the resulting birth be 

 male or female. 8 



8 Loc. Cit. 



