I’ve been wondering about how IQ test designers actually decide whether a question measures intelligence instead of something random. Like, what makes a pattern problem or a vocabulary question “valid” in a psychometric sense?
Basically, what separates a “good” IQ question from one that looks clever but doesn’t meaningfully tell you anything about someone’s cognitive ability?
Validity (is it measuring what it should?) is useless if it doesn’t also have Reliability (does it measure it consistently?).
A question must yield the same results for similar individuals across time and across different forms of the test. This consistency comes from rigorous standardization. Every test administrator must read the exact same instructions, every scoring rubric must be identical, and the conditions must be uniform. If a question is scored subjectively, or if it confuses people on Tuesday but not on Friday, its validity is compromised.
Good IQ questions strongly correlate with overall test performance, give consistent results when retaken, and predict real-world outcomes like school or job success. Test designers run questions on large samples and cut anything that doesn’t consistently separate high from low performers or relate to other intelligence measures. If it doesn’t do those things reliably, it’s just a random puzzle, not a valid test item.
A question is a valid measure of intelligence if it reflects cognitive processes that meaningfully impact a person’s everyday functioning, problem-solving, and adaptability. In clinical practice, we look not just at abstract reasoning, but at whether the task taps abilities that influence learning, decision-making, and coping. A good question is one that helps us understand how someone thinks and processes information in ways that are important to their mental health, daily life, and potential interventions, rather than just producing a numerical score.