1174 EARLE V. HARDENBURG 



frequency of spraying. These factors contributed in some degree to the 

 greater yield apparently resulting from the deeper plowing. In answer 

 to the question whether the deeper plowing was accompanied by deeper 

 planting, it may be stated here that, whereas the Long Island fields were 

 plowed at about the same average depth as those of the similarly light 

 soils of Franklin and Clinton Counties, the average depth of planting was 

 deepest on Long Island, and shallowest in Franklin and Clinton Counties, 

 of the four regions. Apparently, deeper plowing on Long Island is to be 

 advised. 



By virtue of its descriptive value as well as its value as a means for 

 measuring correlation, the biometrical method has been applied to this 

 factor of depth of plowing for Long Island, as also for the other regions, 

 and the result is shown in figure 132. The correlation coefficient, r, here 



Yield per acre, in bushels 



OjpO*O O iO Q *O O *O O O 



"jt^OCM lO b- O C^l ^O t^OtN 



.3 3 



& 4 

 5 



|| 



O O 



. H O 



o- 9 



10 



& 11 



Q 12 



1 6 27 37 81 42 60 27 23 13 83 328 

 r = 0.159 0.036 



FlG. 132. CORRELATION OF DEPTH OF PLOWING AND YIELD ON 328 LONG ISLAND FARMS IN 1912 



has the value 0.159 d= 0.036. Inasmuch as the coefficient is positive and 

 is more than three times its probable error, it shows a significant degree of 

 correlation between depth of plowing and yield. Present-day biometri- 

 cians are now well agreed that the significance of a coefficient is measured 

 not alone by its absolute value, but in the light of its consistency with 

 coefficients of other series or other years and its probable error. 



Depth of plowing in Steuben County 



In contrast to soil conditions on Long Island, the soils of Steuben County 

 are the heaviest of any of the four regions. Nevertheless, a rather marked 

 positive correlation between depth of plowing and yield is shown in table 

 18. In this region, as on Long Island, the growers who plowed deeper 



