# Expected move

**ADV-24 · Advanced Options · Core**

**Lesson question:** What does an option-implied movement estimate mean?

Original fictional examples; educational writing, not live market data, orders or production approval.

## By the end

- Explain the mechanism in the lesson question.
- Reproduce the worked comparison and recognize its failure case.

**Prerequisites:** OPT-F01, OPT-F02, OPT-F03, OPT-F04

An expected-move display needs a declared method. A volatility-based standard-deviation approximation, an ATM straddle premium and a percentile interval are not automatically the same statistic.

No displayed band is a boundary that price cannot cross.

## Understand the mechanism

For a simple short-horizon approximation, S×sigma×sqrt(T) gives a dollar scale associated with volatility. A lognormal model has asymmetric price quantiles after exponentiation, and probabilities require explicit distribution and drift assumptions.

An ATM straddle reflects risk-neutral option pricing, carry and the shape of the payoff; it is not universally one physical-world standard deviation.

## Walk through the process

Read the method, day count, expiry and IV source. Compare a directional forecast with the amount priced, while allowing jumps, skew and model error. Do not claim a certain probability for any arbitrary expected-move line.

For spread selection, crossing a band must remain a possible adverse branch.

## Model and implementation boundary

These are complete fictional reading examples, not live opportunities. Terminal identities assume the stated common settlement. Multi-expiry values require a surviving-leg model. Costs, assignment and financing can alter realized outcomes; a mathematical bound alone does not guarantee the same operational loss path.

## A worked example

At fictional spot100, IV 25% and thirty calendar days, the simple scale is 100×0.25×sqrt(30/365)=7.167277. The linear band 100±7.167277 is only a rough volatility scale under these assumptions.

The graph varies maturity at fixed IV. The widening curve is not a future stock path or a guaranteed confidence interval.

## Calculation popup: Volatility-based movement scale

```text
Scale=S sigma sqrt(T)
```

This is not an unqualified probability interval.

1. S=100; sigma=.25; T=30/365.

2. 100×.25×sqrt(30/365)=7.167277238512.

**Result:** Approximately7.167 dollars.

## Graph: Expected move—worked comparison

**Horizontal:** Calendar days remaining  
**Vertical:** Approximate movement scale (USD)

Fictional data from the written example. The chart organizes the comparison; its shape is not a forecast.

Complete numerical data are embedded in `scripts/advanced-options/ADV-24.js` and displayed as an accessible table in the HTML lesson.

## What would invalidate the reading?

Using a displayed expected move as a guaranteed range can make short-wing risk look smaller than it is. Mixing trading and calendar days changes the scale.

## Check your understanding

### What is the thirty-day scale in this example?

**Answer:** About 7.167 dollars.

**Why:** Its statistical interpretation still depends on stated assumptions.

### What is the critical failure to avoid?

**Answer:** Using a displayed expected move as a guaranteed range can make short-wing risk look smaller than it is. Mixing trading and calendar days changes the scale.

**Why:** Explain this risk before treating the example as a decision rule. A correct calculation does not guarantee a favorable market outcome. **Critical risk check.**

## Takeaway

Return to the question: What does an option-implied movement estimate mean? State the observed facts, the assumptions and the failure condition separately.

## References and provenance

The cited references support definitions and conventions. The teaching prose, tickets and numerical scenarios are original; they are not attributed as historical market observations.

- [OIC Strategy Reference](https://www.optionseducation.org/strategies/all-strategies-en)

- [OCC Options Disclosure Document](https://www.theocc.com/company-information/documents-and-archives/options-disclosure-document)

- [OIC Greeks](https://www.optionseducation.org/advancedconcepts/understanding-options-greeks)