A STUDY OF FACTORS INFLUENCING THE YIELD OF POTATOES 1147 



BIOMETRY AS APPLIED TO CROP-SURVEY DATA 



Biometry as a science is beginning to have wide application, wherever 

 sufficient data make its application possible, in the solution of problems 

 involving the study of the interrelation of factors or the study of cause 

 and effect. Until the present time, biometry has been used mainly only 

 in the study of inheritance and in the correlation of characters in large popu- 

 lations of plants and animals. Its use has been thus limited because only in 

 such studies have conditions been so controlled that none but the factor or 

 factors under observation could affect the results, and because it has been 

 possible to use large numbers of individuals for such investigations. 

 Biometry should have a place in the study of crop-survey data wherever 

 large numbers of records are involved, in order that the coefficient of 

 correlation may serve as a check on the conclusions otherwise drawn and 

 that it may furnish, thru its frequency table, a description of the prevailing 

 practice in the region in question. 



Tolley (1917) states that the coefficient of net correlation affords a 

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

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

 to find the true relationship between any two. Applying biometrical 

 methods to farm-survey data on fattening baby beef, Tolley has shown 

 how the 'gross apparent correlation between any two or more factors may 

 be substituted in a derived formula and the net correlation of any two 

 factors thereby deduced. - r ^'l 



A biometrical analysis of some of the more influential factors involved in 

 this study has" been made, altho, owing to the relatively large numbers of 

 records used in each study, only the gross correlation has been computed. 

 Aside from the actual significance of the coefficients obtained, much 

 information of descriptive value relative to the frequency of a given 

 practice may be found in the frequency distribution tables. One of 

 the chief functions of biometry is description. It affords a means of 

 classifying a group of individuals not possible by any other means. 



THE TAKING OF RECORDS 



Five men constituted the party employed in the taking of records in 

 1913. This made it possible for four of the party to travel thru the 

 potato regions in pairs while the fifth man copied and checked each day's 

 records. In this way, any discrepancies in the records could be checked 

 up by a return visit to the grower or by discussion within the party. The 

 data on the 1913 crop were taken in 1914 by two ,men. 



As previously noted (Spillman, 1917), the value and accuracy of survey 

 data depend largely on freedom from bias. This may well apply to thje 

 selection of farms to be observed. Therefore it was decided that for these 

 surveys the only limitation in the selection of a farm was to be in. the 

 acreage of the crop produced the previous year. This limitation was set 



