Percentile (p10 / p50 / p90)
p10 / p50 / p90 are the price levels that 10%, 50%, and 90% of simulated paths end below.
A percentile splits a distribution by the share of outcomes that fall below it.
- p50 — the median. Half of paths end above this price, half below. The centre of the simulated cone.
- p10 — only 10% of paths end below this level. A reasonable proxy for a “bad-case” downside.
- p90 — 90% of paths end below; only 10% end above. A reasonable proxy for an “upside stretch.”
The interval from p10 to p90 contains 80% of simulated outcomes. It is not a guarantee — 1 path in 5 still ends outside this range — but it's the most common way analysts summarize a probabilistic forecast.
See also: Monte Carlo Simulator, Sigma (σ), Monte Carlo Simulation