AAPL332.21-0.06 (-0.02%) session● PRIOR SESSION CLOSE
probability distribution — a realized-vol estimate, explained
Estimated price-outcome distribution at expiry
An estimated probability distribution, centered on the live spot and built from AAPL's own realized volatility (how much it has actually moved) — where it could sit at expiry given that, not a forecast. The volatility level is a realized-vol estimate and the skew shape is modeled — neither is market-implied. With the mean, mode and median, the probability above versus below spot, an arbitrage-free check, and notes on each figure.
AAPLspot $333.08realized vol 31.9%arbitrage-free ✓realized-vol estimate · skew modeled
Likely range at expiry$310.60 – $370.55 — the 16th–84th percentile (68%) band, read off the estimated distribution; spot $333.08.Two ways of measuring the same spread: half the band above is $29.97, while the distribution's own typical swing is $30.40 — a quantile band and a moment need not match on a curve leaning -0.33; both are read off the same served grid.
estimated density68% rangespotmedian
Mean (realized-vol est.)$334.18
Mode (most likely)$340.57
Median$335.76
P(below spot) at expiry46.4%
P(above spot) at expiry53.6%
Horizon30d
1-σ swing (±)$30.40
Skew-0.33
Probability mass1.000
realized vol 31.9%63d close-to-closeannualized ×√2521-σ $30.4030d horizonmoments of the served density grid (trapezoid)skew -0.3330d horizonthird moment of the served density grid (trapezoid)mean $334.1830d horizonBreeden-Litzenberger density · modeled skew shape
AAPL's realized volatility puts the most-likely landing near $340.57 with a $30.40 one-sigma swing, a left-skewed shape, and is arbitrage-free. The agent below explains how a vol level and a strike grid become a probability distribution, and how that curve weights a strategy's payoff. The vol level is a realized-vol estimate from daily closes and the skew shape is modeled — neither is read off the chain's quoted implied vols, so neither is market-implied; the Breeden-Litzenberger math is real. Your decisions, your risk.
Each card walks one piece of the distribution — what it shows, what the math means, and what it suggests — so a beginner can read this realized-vol probability curve.
What is this probability distribution?
Built from AAPL's realized volatility, the most-likely landing is near $340.57 (the peak), with a mean of $334.18 and a one-sigma spread of about $30.40.
A volatility level + a strike grid, run through Breeden & Litzenberger (1978), becomes an entire probability distribution: line up call prices across strikes and the curvature of that line literally IS the density. The peak is the most-likely landing spot; the width is how uncertain the move is. Here the vol level is a realized-vol estimate from daily closes — not the quoted implied vols on the options chain, so it is not market-implied.
→ Most-likely close ~ $340.57; a realized-vol estimate of a $30.40 one-sigma swing.
How the skew bends the distribution
The distribution is left-skewed (fatter downside tail — more weight on a downside surprise) and close to a normal bell curve in the tails. Skewness -0.333, kurtosis 3.2467.
A flat-IV (one number for every strike) world gives a clean lognormal bell. Real markets charge MORE implied vol for downside puts — that "skew" fattens the left tail of this curve, so the distribution leans toward downside surprises. The shape of the IV smile is the shape of the fear.
→ Downside protection is bid — the left tail is fat.
Is the curve arbitrage-free?
Yes — the call-price curve is convex everywhere, so every recovered probability is non-negative.
Probabilities can never be negative. Mathematically that requires the call-price curve to be CONVEX (bend upward) across strikes. If a middle call is too cheap relative to its neighbors, the second difference goes negative — a free-lunch "butterfly" arbitrage. The lab checks this automatically.
→ No-arbitrage: the recovered density is valid.
More on this screen (1)
From distribution to expected value
Under this curve a payoff near $340.57 carries the most weight and one beyond a $30.40 move carries far less — that probability-weighting, minus what the trade costs, is its expected value.
Expected value is a strategy's expiry payoff integrated against a probability distribution, minus the premium. This distribution is one estimate, built from a realized-vol level — where your own read of the landing zone disagrees with it is exactly where the positive-expected-value structures sit.
→ Positive-EV hunting: where your view and this estimate disagree.
Glossary — 6 terms
- Risk-neutral density
- The probability distribution of where the stock lands at expiry, backed out from option prices (not a real-world forecast — it is the price-weighted one).
- Breeden-Litzenberger
- The 1978 result that the density equals e^{rT} times the second derivative of the call price with respect to strike.
- Skewness
- Asymmetry of the distribution; negative = fatter downside tail.
- Kurtosis
- Tail-fatness; above 3 means more extreme moves than a normal bell curve.
- Butterfly arbitrage
- A non-convex call curve implying a negative probability — a riskless mispricing.
- Expected value (EV)
- The probability-weighted average P&L of a trade: payoff integrated against the distribution, minus cost.