What is a CI90 confidence interval in a stock forecast?
CI90 — the 90% confidence interval — is the price range between the 5th percentile (q05) and 95th percentile (q95) of every simulated path the quantum model produces for a ticker at a given horizon. If the model is well-calibrated, about 90% of realized prices should land inside this band over many forecasts — the other roughly 10% land outside it, by design, not by error. A wide band means the model sees genuine uncertainty; a narrow band means conviction. Neither width is inherently good or bad on its own: a band that never gets missed is usually too wide to be useful, and a narrow band that gets missed often is overconfident.
What CI90 does not tell you
Coverage is not the same as being right. A price landing inside the band means the outcome was covered, not that the model's central estimate correctly called the direction or magnitude of the move. A band can fully contain the realized price while the mean forecast points the opposite way. CI90 also says nothing about whether a trade based on the forecast would have made money — that depends on entry price, position size, and exit discipline, not band width alone.
Live example: as of the last scan, AAPL's 3-month CI90 band is $304–$401 around a current price of $309 (above the current price by 12.2% at the mean). See the full AAPL forecast.
How Quantustik checks its own CI90 bands
Rather than asserting calibration, Quantustik publishes it: the live calibration page reports actual CI90 coverage per forecast horizon against the committed TOP-20 backtest, including the misses. Following the #1088 horizon-dependent recalibration, coverage lands within the well-calibrated 85–95% range at every horizon, though per-ticker dispersion is still wide for structural-break names.
Frequently asked questions
What does a 90% confidence interval mean for a stock forecast?
It means the model expects about 90% of realized prices to land inside the published band over many forecasts — not that the forecast is "right" 90% of the time, and it says nothing about direction.
Is a wider CI90 band worse than a narrow one?
Not by itself. A wide band reflects genuine uncertainty (e.g. an earnings-week ticker); a narrow band reflects model conviction. What matters is whether the band's actual coverage matches its stated 90% — see the calibration page for that check.
How is Quantustik's CI90 calibration checked?
Against a committed, reproducible TOP-20 S&P 500 backtest, published on the live calibration page with the misses shown alongside the hits — not just an aggregate average.
Does CI90 predict direction?
No. CI90 is a coverage promise about the price range, separate from whether the model's mean forecast points up or down.
Educational research only — not investment advice.