Converting GRE verbal scores to IQ’s

Posted on 5 February 2009

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A short while ago, I did a linear regression on LSAT scores and IQ’s to make a comparison. I am now doing the same thing to compare GRE Verbal scores to IQ’s.

The GRE verbal section correlates better with traditional IQ tests than its other sections.  From the Prometheus report on test acceptances (Section 8.6.5):

The GRE is comprised of three subtests: Verbal, Quantitative and Analytic sections. Each GRE score is a value that is independent of when the score was obtained. Scores are “scaled” based on performance on the test and the properties of the individual test itself. All General (Aptitude) Test scores are reported on this same scale. A verbal ability score of 550 earned in 1972 will, therefore, for example, be equivalent to a verbal ability score of 550 earned in 1982. Several different editions, or forms, of the General (Aptitude) Test are in active use in the GRE program at any given time. Over several years many different forms will be used. Compensation for variations in difficulty among these forms of the test are taken into account when the number of correct answers are converted to the scaled score. This supports direct comparisons of performance of examinees taking different forms of the test . . .

. . . The GRE is somewhat similar to the SAT in having a wide constituency in the United States and in having verbal and mathematical subtests. It has been shown to correlate well with many standard IQ tests such as (the verbal subtest) with the MAT and in the combined score pairs reported in the norming data for the Mega reported above . . .

The SAT verbal section correlates with traditional IQ tests at .8, which, at that correlation (only IQ tests correlate with each other at that level), makes the SAT verbal section nothing less than an IQ test.  The GRE verbal section is harder than the SAT verbal section; it’s reasonable to think that the GRE verbal section correlates just as well with traditional IQ tests.

However, the SAT quantitative section correlates with traditional IQ tests at no more than .7, which makes it a weaker measure of intelligence (though it still is pretty good).  The GRE quantitative section is much easier than the SAT quantitative section.  So it’s reasonable to think that the GRE quantitative section correlates even less than .7 with traditional IQ tests.

The moral of the story is that the GRE Verbal section is a great measure of intelligence for those who are native, or non-native, well-versed, English speakers.

So I scoured the high IQ societies and found that a number actually accept the GRE verbal section by itself.  The ISI-Society does so with two points: a 790 verbal score is equivalent to a 148 IQ, and a 700 verbal score is equivalent to a 137 IQ (assuming SD is 15). I’m taking these two point from this one society for the internal consistency. My third point comes from the verbal score average—historically about 470—corresponding to a college graduate average IQ of 105. Having more points would be better, but this will work for now.

My slope is 0.13531211750306, and my intercept is 41.5960832313339.  We can round them to .135, and 41.596.  The resulting equation is IQ = .135*Verbal + 41.596.  The following is a incomplete chart; the decimal places don’t imply greater accuracy:

800            +148

790            148

780            147.139534883721

770            145.78641370869

760            144.43329253366

750            143.080171358629

740            141.727050183599

730            140.373929008568

720            139.020807833537

710            137.667686658507

700            137

690            134.961444308446

680            133.608323133415

670            132.255201958384

660            130.902080783354

650            129.548959608323

640            128.195838433293

630            126.842717258262

620            125.489596083231

610            124.136474908201

600           122.78335373317

I would advise anyone using this chart to drop the decimal points.  For example, if you scored a 630 verbal score, then take your IQ to be roughly 126 and neither a 126.8 nor 127.

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Posted in: GRE, IQ, LSAT