I’ve always heard that IQ scores are supposed to be stable, but I’m not totally sure how many data points you actually need before you can trust that a score is “real.” If someone takes one official test and gets a 122, is that enough to assume that’s their true ability? Or should they retest after a while to make sure it wasn’t just a good or bad day? Basically, how much retesting does it take before a score is considered solid?
A single properly administered test is generally considered sufficient for most purposes. IQ tests like the WAIS have high test-retest reliability (around 0.90+), meaning scores are quite stable. The score comes with a confidence interval, so a 122 might really mean “between 117-127 with 95% confidence” which already accounts for measurement error. Retesting immediately would actually be problematic due to practice effects (people score higher on retests just from familiarity). If you did want to confirm, you’d wait at least 6-12 months or use a different test. But for clinical or educational purposes, one well-administered test is typically trusted.
Reply: One properly administered test is usually enough—IQ scores are pretty stable with a test-retest reliability of around 0.90+, meaning if you score 122 once, you’ll likely score within 5 points of that on a retest. That said, if you suspect the testing conditions were off (sick, anxious, distracted) or the score seems way different from your expectations, a second test can be helpful. Psychologists generally trust a single well-administered test, but two tests with consistent results give even more confidence. Beyond two tests, you’re mostly just seeing the same number with minor fluctuations.
Professional IQ tests are designed to minimize day-to-day variation. For a typical test day to significantly shift your score, you’d need something genuinely disruptive like illness, severe sleep deprivation, or extreme anxiety. Normal fluctuations from being a little tired typically produce changes of only 3-5 points, which fall within the test’s measurement error anyway. If your score feels surprisingly high or low, maybe the issue isn’t the test’s accuracy but rather miscalibrated expectations? Like comparing yourself to a selective peer group, or underestimating based on school struggles that reflected non-IQ factors.