UNITED STATES DEPARTMExNT OF AGRICULTURE 



BULLETIN No. 504 



OFFICE OF THE SECRETARY 



Contribution from the Office of Farm Management 



W. J. SPILLMAN, Chief 



Washington, D. C. 



PROFESSIONAL PAPER 



May 23, 1917 



THE THEORY OF CORRELATION AS APPLIED TO FARM- 

 SURVEY DATA ON FATTENING BABY BEEF. 



By H. R. ToLLEY, Scientific Assistant. 



CONTENTS. 



Introduction 



Theory of correlation 



Computation of the coefficients 



Page. 

 1 

 1 

 6 



Interpretation of the coefficients _. 

 Summary 



Page. 



8 



13 



INTRODUCTION. 



This paper sets forth the results of an experiment in applying the 

 theory of correlation, hitherto used chiefly in the analysis of biologi- 

 cal, sociological, psychological, and meteorological statistics,^ to the 

 study of some of the data of the Office of Farm Management. 



The material for the investigation was obtained from 67 records 

 taken during the years 1914 and 1915 from farmers of the corn belt 

 who were fattening baby beef for market.^ The factors considered 

 were: The profit or loss per head, the weight, value per hundred- 

 weight, value of feed consumed per head, cost at weaning time, and 

 date of sale (see Table I). Coefficients of correlation were computed 

 for every pair of these factors and used as a measure of the relation- 

 ship existing between them. 



THEORY OF CORRELATION. 



The writer will not attempt a detailed explanation of the theory 

 of correlation but will discuss briefly the meaning of coefficients of 

 correlation and the method by which they are obtained. 



1 Yule, G. U. : " Introduction to the Theory of Statistics," 1912. Yule, G. U. : " On the 

 Theory of Correlation," Jour. Roy. Stat. Soc, 1897, p. 812. Davenport, C. B. : " Statisti- 

 cal Methods, With Special Reference to Biological Variation," 1914. Hooker, R. H. : 

 " The Correlation of the Weather and the Crops," Jour. Roy. Stat. Soc, 1907, p. 1. 

 Smith, J. W. ; " Effect of Weather on Yield of Corn," Monthly Weather Review, vol. 42, 

 p. 72 ; and " Effect of Weather on Yield of Potatoes," ibid., vol. 43, p. 232. Brown, Wm. : 

 " Essentials of Mental Measurement," 1911. 



2 For detailed account of the methods by which these data were obtained and the costs 

 computed, see Report 111, Office of the Sicretary, 1916. 



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