412 



MEMOIRS NATIONAL ACADEMY OF SCIENCES. 



[Vol. XV, 



The starred tests of the above list are the ones selected for the abbreviated scale. They 

 are not in all oases the tests having highest diagnostio value, since it was necessary to consider 

 time required to give a test, suitableness for illiterate subjects, and desirability of obtaining 

 a short scale oomparable in difficulty throughout its range with the entire scale. The average 

 of the ratios in the last column of Table 69, for the starred tests, is practically the same as 

 the average of the ratios for the entire scale, the former being 53.9 per cent and the latter 55.9 

 per cent. The average score for the entire scale is 53.3; for the abbreviated soale, 26.6. The 

 average percentage of zero scores for the whole scale is 18.4; for the abbreviated scale, 12.9. 



The total score on the abbreviated soale is 50 points. Records of 476 men were rescored 

 on the abbreviated scale and the soores obtained multiplied by 2. The deviations of the 

 short soale scores in points from the scores on the entire scale were as follows: 



The median deviation was 3 points, and the mean deviation 4.14 points. Since the yearly 

 ncrements in points beginning with mental age 5 are 6, 7, 6, 9, 8, 6, 6, and 4, up to mental 

 age 13, it will be seen that the median deviation of 3 points corresponds to approximately 

 a half year in mental age from 5 to 8, about a third of a year from 8 to 10, a half year from 10 

 to 12, and three-quarters of a year at 13. The corrresponding median deviation of the short 

 form of the Stanford-Binet was three-tenths of a year. 



The correlation of abbreviated with complete Point Soale for the 475 subjects, ranging 

 in mental age from 4 to 18 years, was 0.934 (Pearson). When subjects above 12.5 mental age 

 were excluded, in order to make the coefficient of correlation comparable with that for the 

 abbreviated Stanford-Binet (which extends only to 12.5 years), the correlation was reduced 

 from 0.934 to 0.913. (Corresponding figure for Stanford-Binet, 0.912.) 



Table 70. — Correlation of brief with complete point scale. (r. = .9S4-) 



Certain important faots in the above correlation arrays are summarized in tables 71 and 72. 

 Table 71. — Median scores (computed) on whole scale for subject making each score on each test. 



i Tests selected lor short scale. 



