Correlations between two forms of the same test (up to 0.94, averaging 0.83 in Colvin's data) far exceed between-test correlations, casting doubt that different 'general intelligence tests' measure the same element¶

Claim · All claims
Evidence · 1 study · associational r1 · q2
Currency · newest study 1921 · not yet checked against its sources · not reviewed by a person

Subclaims¶

q2 i? Reported correlations between two forms of the same test (Otis Forms A and B from 0.74 to 0.94; Snarr 0.79; Colvin averaging 0.83) are much higher than correlations between different tests, leading the author to doubt the tests measure the same element. → Geyer 1921

Evidence¶

Geyer 1921¶

Geyer, D. L. (1921). The Reliability of Rankings by Group Intelligence Tests. The Journal of Educational Psychology. https://www.jstor.org/journal/jeduapsy

q2 · i? · associational · r1

The author's interpretive comparison of cited form-reliability figures (Otis 0.74-0.94; Snarr 0.79 with 306 pupils; Colvin averaging 0.83; Brown halves 0.76) against the between-test correlations reported earlier in the article.

"Comparing this agreement with the wide variation cited above leads one to doubt somewhat that the different tests, though all called "general intelligence tests," are really measuring the same element in the pupil's endowment."

Discussion¶

Related Claims¶

• Group intelligence scores correlated only modestly with school marks (freshmen: 0.41 Thurstone, 0.56 Brown; junior high: 0.25 Illinois, 0.32 Otis), which the author attributes to marks depending on many non-intelligence factors — related
• Rankings of the same 120 junior high pupils by the Otis and Illinois group intelligence tests disagreed by a median of 18 places, with a rank correlation of 0.642 — a narrower finding that bears on this claim
• Thurstone-Brown agreement was closer than Otis-Illinois: median rank changes of 6.7 places (freshmen, r = 0.74) and 10.4 places (sophomores, r = 0.613), with 26 and 32.8 per cent wrongly classed — related