Judith,
I would guess that the 100 comes from the original method of calculating IQ....MA/CA *
100 (MA = mental age; CA = chronological age). Multiplying by 100 gets rid of
decimals and makes 100 the criteria for age-appropriate levels. When they changed to
derived scores, they may have wanted to keep some consistency.
A fascinating resource on the history of IQ testing would be Stephen Jay Gould's The
Mismeasure of Man. I don't think it does current psychometric theory justice, but it
is loaded with important and recurring issues in testing.
Mark
Mark J. Sciutto, Ph.D.
Dept. of Psychology
Westminster College
New Wilmington, PA 16172
[EMAIL PROTECTED]
