Commenter Mary has been bugging me to continue my revised new GRE series:

In today’s class, we’ll estimate the average IQ of Americans who take the GRE (and by proxy other graduate school admission tests like the LSAT, GMAT, and MCAT).

In a study of  22,923 students who took the GRE circa 1984 and the SAT circa 1979.5, the following SAT scores were observed: Verbal 518.8 (SD = 104.7) and Math 556 (SD = 110.2).  The combined SAT scores were not reported, but by summing the Verbal and Math means, we can estimate the combined mean was 1074.8 and from the 0.628 correlation between the SAT Math and Verbal in this sample, we can estimate the combined SAT had an SD of 193.9 in that sample.

In order to convert these SAT scores to IQ equivalents, we need to know how all U.S. 17 year olds would have scored on the SAT in 1979.5, including the many who dropped out long before graduating from high school, or even elementary school.

I don’t know how all U.S. 17-year olds would have scored on the SAT in 1979.5, but the nearest year for which I have good data is 1983, and that year, all U.S. 17-year-olds would have scored Verbal 376 (SD = 116), Math 411 (SD = 124) and combined 787 (SD = 220).  If we convert those three distributions to the IQ scale (mean = 100; SD = 15), then GRE takers had the following IQs: Verbal 118 (SD = 13.5), Math 118 (SD = 13.3) and Combined 120 (SD = 13.2) (U.S. norms).

Postscript:

It’s worth noting that the above stats are quite dated.  In the 20th century, a smaller percentage of people graduated from college and thus took the GRE.  For example in the 1995 norming of the WAIS-III, Americans with 16+ years of education had a median full-scale IQ of 112 (see table 8) but in the 2006 norming of the WAIS-IV, the mean is about 111 (see table 4.1); a drop of one point as university has become more democratized.

Thus people who took the new GRE probably have IQs about one point lower, so for these I would estimate the following IQs: Verbal 117 (SD = 13.5), Math 117 (SD = 13.3) and Combined 119 (SD = 13.2).

Now that we know the IQ distribution of Americans who take the GRE, converting their GRE scores to IQ is easy.  And we will take that final step in part 3.