COREELATION AS APPLIED TO FARM-SURVEY DATA. 13 



These rather large coefficients become very little smaller when all the 

 other causal factors are taken into account. Therefore, there must 

 be some relationship existing between value per pound and date of 

 sale, and value per pound and value of feed consumed. The reason 

 for the correlation between value per pound and date of sale has 

 already been given. It is probable that the reason for the high corre- 

 lation between the value per pound and value of feed consumed is 

 due to the fact that the calves which were fed the heaviest ration, 

 regardless of the length of feeding period, were the fattest when 

 marketed, and consequently sold at a higher price. However, the 

 relation between the profit and value of feed consumed per head as 

 measured by the correlation coefficient r^f is — .27, and when the in- 

 fluence of a longer feeding period is taken into account by elimi- 

 nating the effect of date of sale the correlation is still negative 



SUMMARY. 



The results show that data such as those obtained by farm manage- 

 ment surveys can be analyzed very thoroughly by the use of the corre- 

 lation coefficients. It is generally known before the analysis is at- 

 tempted which factors are causal and which resultant, and conse- 

 quently there should be verj^ little difficulty in interpreting the coeffi- 

 cients correctly. The coefficients of net correlation afford a very good 

 means of determining the net effect of each of several factors bearing 

 upon a result, or of eliminating the effect of other factors when it is 

 desired to find the true relationship existing between any two. 

 Although it is not possible to give a definite concrete meaning to cor- 

 relation coefficients, they are very concise relative measures of the 

 degree of relationship existing between the factors being studied. 

 They therefore give the investigator a single index which will show 

 what, by the ordinary tabular method, it takes a whole table to show. 

 While properly constructed tables will show whether or not any rela- 

 tionship exists between two factors, it is a difficult matter to deter- 

 mine which of two causes, say, has the greater effect on the result, and 

 it is impossible, without a large number of records and a great amount 

 of sorting and tabulation, to separate all the factors being considered 

 in a study and find the effect that each one would have had if the 

 others had not been present, or if they had been constant throughout 

 the investigation. If the gross coefficients of correlation between 

 every pair of factors have been determined, it is possible to find these 

 relationships by simply substituting in the formula for determining 

 a net coefficient from the gross coefficients, without any further refer- 

 ence to the records themselves. This method should be especially use- 



