administration must also establish a basal age for each test: the lowest level or point where two consecutive items of approximately equal difficulty are passed. Testing then proceeds within each test until ceiling is reached: the point at which at least three out of four items are missed. The concept of age differentiation is retained, in that within each test, items are presented in order of increasing difficulty roughly according to their ability to discriminate different age groups.
The modern Binet scale retains the use of standard scores. Raw scores on each of the 15 test can be converted to standard age score with a mean of 50 and a standard deviation of 8. The grouping of individual tests into content areas permits one to calculate four area-content scores, each with a mean of 100 and standard deviation of 16. A composite score that reflects general mental ability and that is based on the tests given to an an individual is also calculated. The mean of this composite is also 100 (SD=16)as in the deviation IQ of the 1960 version. (See Figure 10-10.)