Interpreting results · 2026-05-15 · 6 min lesetid
By Brain Test Editorial · Last updated 15 May 2026
When you finish a cognitive test, you usually see at least three numbers: an IQ estimate, a percentile, and sometimes a confidence interval. They look similar but they answer very different questions.
Percentile in one sentence
A percentile tells you what share of the reference population you outscored. If your percentile is 84, you scored higher than 84 % of people in the comparison group — and 16 % scored higher than you.
Why percentiles feel surprising
Most cognitive scores follow a roughly bell-shaped (normal) distribution centred on 100, with a standard deviation of 15. That means small jumps near the middle of the curve cover a lot of people, while big jumps near the edges cover very few. The same 10-point gap means very different things depending on where you start:
- IQ 100 → IQ 110: moves you from the 50th to the 75th percentile (about 25 percentage points).
- IQ 130 → IQ 140: moves you from the 98th to the 99.6th percentile (less than 2 percentage points).
This is why a high IQ score sounds impressive but corresponds to a very thin slice of the population.
Confidence intervals: honest uncertainty
No single test can pin down your "true" ability exactly. A 95 % confidence interval is the test's way of saying: "Given the measurement error, your true score is probably somewhere in this range." A reported IQ of 115 with a 95 % CI of 109–121 means there is a 95 % probability the underlying ability falls in that band — not that you scored exactly 115.
What this means for you
- Don't fixate on a single point estimate.
- Read the percentile as a rough position in the population, not a precise ranking.
- If two test results overlap within their confidence intervals, they are statistically the same.
Brain Test shows both an IQ estimate and a percentile so you can see your position from both angles. For a deeper dive into how the score is calculated, see the about page.