WORDSUM and IQ, and their Correlation

Often I’ve seen people use WORDSUM scores as a proxy for IQ. You may have seen it yourself, but wondered why people believe there is a correlation between the two. Razib Khan wrote up a nice post that explains it.

Every time I use the WORDSUM variable from the GSS people will complain that a score on a 10-question vocabulary test is not a good measure of intelligence. The reality is that “good” is too imprecise a term. The correlation between adult IQ and WORDSUM = 0.71. The source for this number is a 1980 paper, The Enduring Effects of Education on Verbal Skills.

Jason Malloy further makes the comment that…

I’ve linked this paper before as well. The WORDSUM is an IQ test, and not simply a “proxy” for IQ, as many have called it. This is determined by its construct validity.

It’s clearly tapping a cognitive dimension; vocabulary strongly correlates (.83) with the general intelligence factor: content validity. The WORDSUM correlation with the AGCT is within the range that IQ tests correlate with each other: concurrent validity. It is a reliable independent predictor and predicts external outcomes in a similar manner as other IQ tests: criterion validity.

I wouldn’t recommend it for clinical or admissions purposes, but the GSS is an adequate cognitive test for the purposes of the GSS.

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