The Open-Source Psychometrics Project
The Open-Source Psychometrics Project is an online platform that has hosted dozens of public-domain personality and ability tests since 2011, including a 25-item adaptation of Raven's Progressive Matrices, a verbal IQ scale, and a culture-fair intelligence test. Each completed test contributes anonymized data to a public dataset that can be downloaded freely for research.
The Open-Source Psychometrics Project is an online platform that has hosted dozens of public-domain personality and ability tests since 2011, including a 25-item adaptation of Raven's Progressive Matrices, a verbal IQ scale, and a culture-fair intelligence test. Each completed test contributes anonymized data to a public dataset that can be downloaded freely for research.
Sub-test design is one of the most carefully studied areas of psychometrics. The goal of any subtest is to measure a specific cognitive ability with high reliability while minimizing confounds with unrelated abilities, prior knowledge, and test-taking strategy. Achieving that goal requires substantial effort: items must be piloted on large samples, item-response-theory parameters estimated, and the resulting items selected for inclusion in the operational test.
Modern subtests are typically scored using item-response theory (IRT) rather than simple sum scores. IRT produces ability estimates that account for the difficulty of each item and the discrimination of each item — how well it separates high-ability from low-ability test-takers. The resulting scores are more precise than raw counts and allow direct comparison across alternate forms of the same test.
For The Open-Source Psychometrics Project, the underlying cognitive demand is well-characterized in the research literature. Strong performers typically employ specific strategies that can be partially taught, which is one reason the test is moderately coachable. The size of the practice effect depends on the test-taker's starting level, the amount and structure of practice, and the similarity between practice items and operational items.
Public-domain item pools — particularly the ICAR catalog and the items released by the Open-Source Psychometrics Project — make it possible to study these subtests in academic research without paying licensing fees to commercial publishers. This site's free screener uses original items modeled on these public conventions.
If you are particularly interested in this subtest, you can take a longer dedicated assessment via the public-domain projects linked in the Related Reading section. Single-domain assessments provide more precise estimates of the specific ability than the brief multi-domain screener used here.