26 BASES FOR CURRICULUM MAKING 



of subject-matter, how much time should be devoted to develop- 

 ing farm skills, how much to training in carpentry, engine repair, 

 and the like. What is the "pure" relation, we are anxious to dis- 

 cover, between success in farming and field and chore skills? 

 The following formula 14 provides a method of getting rid of 

 the purely mechanical part of the relation and r(fk) :c may 

 be read as the correlation between financial success and field 

 and chore skills with mechanical ability eliminated, equalized 

 or controlled: 



r(fk)-[f(fc)Xr(kc)] 

 r(fk) :c= 



VI r(fc) 2 VI r(kc) 2 

 Substituting the above values in this equation, it takes the form : 



.677 (.472X-654) 

 r(fk) :c=- 



.8827X7599 



Solving, r(fk) :c=.549. This indicates that there was some 

 confusion or constant error the total correlation r(fk) .677 

 being in this case reduced in value to .548. On the other hand, 

 what effect may a conception of skills have on a conception of 

 mechanical ability? Solving similarly we find r(fc) :k=.052. 

 This is rather startling. Does it mean that no mechanical abil- 

 ity is needed on the farm? Obviously not, but it may mean 

 that a peculiar type of mechanical ability is needed that tends in 

 rating to get badly mixed with skills. At least, it opens up the 

 question of kind of mechanical ability and any one familiar with 

 actual mechanical knowledge needed in operating a farm knows 

 that carpenterial ability as shown by a cabinet maker or house 

 carpenter is not particularly desirable. Moreover, one may im- 

 mediately call to mind instances where mechanically-minded 

 farmers who purchased threshing rigs often finally lost not only 

 their machines, but their farms as well. Suffice this correlation 

 to show that the question needs attention if we ar.e to devise 



14. See "An Introduction to the Theory of Statistics" by G. 

 Undy Yule, Chas. Griffin & Co., Ltd., London ; Chapter on Par- 

 tial Correlations ; also Mental and Social Measurements by E. L. 

 Thorndike, pages 180-182; and Educational Guidance, T. L. 

 Kelly, Ph. D., Teachers College Contributions to Education. 



