Haggerty: Study in Arithmetic 



451 



Measured by this standard no one of the cities is doing ''good 

 -work." A variability of 16 per cent is the low mark (city 17, 

 grade 7, subtraction, attempts), and but fourteen times out of 

 a possible six hundred forty is the variability below 20 per cent. 



50 



40 



30 



\VER.\GE 

 R IGHTS 



ATTEMPTS 



YVL22 - y.\Rimun series e grade o si btraction 



It ranges in the other direction to 107 per cent and a mark of 50 

 per cent is not unconmion. In three cases in thirty-two, the city 

 average is above fifty. 



"Whether or not a high variability within a class is bad de^Dends 

 somewhat upon the methods of teaching. Methods are conceivable 



