the expected move and the normal distribution

Selling Premium with Statistics

By:Dr. Jim Schultz

Today's Lesson: Understanding the versatility of Implied Volatility

  • Implied volatility is used to not only price options, but also to build the anticipated ranges of a stock.
  • In statistics, the observations in a normal distribution will fall between +/-1 standard deviation 68% of the time.
  • Knowing the connection between the expected move and normal distribution is quite useful in selling premium.

Implied volatility (IV) in the market might be the most versatile metric of all. Not only is it used to approximate the fear in the market and determine option prices themselves, but it is also used to forecast the anticipated range of stock price movement for any stock in the market—a calculation more commonly referred to as the expected move.

Generally speaking, if Apple (AAPL) has an IV of 40% over the course of a given expiration cycle, and International Business Machines (IBM) has an IV of 20% over the course of that same expiration cycle, then the market is anticipating AAPL stock to be twice as volatile as IBM. In other words, the expected move for AAPL will be much wider than the expected move for IBM, as the higher IV is making room for potentially wilder swings on either side of the market. 

Connection to statistics

The expected move derives its name from statistics, and more specifically the normal distribution. Given enough occurrences and over a long enough time window, stock price movements always fall into a normal distribution, or bell curve, and approximately 68% of the time, the observations in a normally distributed data set will fall within the range of -1 to +1 standard deviation.

Expected moves and short options

This is no coincidence, as it maps perfectly into the expected move. The lower end of the expected move always maps to the -1 standard deviation marker, and the upper end of the expected move always maps to the +1 standard deviation marker. As premium sellers, this is incredibly valuable information, as we look to build our trades, analyze our strategies, and ultimately select our strikes. For example, by selling premium around the expected move in something like a short strangle, we know that our probability of profit on that strategy will be around 68%—given that the probability of that +/-1 standard deviation is the same 68%.

Jim Schultz, a quantitative expert and finance Ph.D., has been trading the markets for nearly two decades. He hosts From Theory to Practice, Monday-Friday on tastylive, where he explains theoretical trading concepts and provides a practical application of those concepts to a trading portfolio. @jschultzf3

For live daily programming, market news and commentary, visit tastylive or the YouTube channels tastylive (for options traders), and tastyliveTrending for stocks, futures, forex & macro.

Trade with a better broker, open a tastytrade account today. tastylive, Inc. and tastytrade, Inc. are separate but affiliated companies.


Options involve risk and are not suitable for all investors. Please read Characteristics and Risks of Standardized Options before deciding to invest in options.

Related Posts

tastylive content is created, produced, and provided solely by tastylive, Inc. (“tastylive”) and is for informational and educational purposes only. It is not, nor is it intended to be, trading or investment advice or a recommendation that any security, futures contract, digital asset, other product, transaction, or investment strategy is suitable for any person. Trading securities, futures products, and digital assets involve risk and may result in a loss greater than the original amount invested. tastylive, through its content, financial programming or otherwise, does not provide investment or financial advice or make investment recommendations. Investment information provided may not be appropriate for all investors and is provided without respect to individual investor financial sophistication, financial situation, investing time horizon or risk tolerance. tastylive is not in the business of transacting securities trades, nor does it direct client commodity accounts or give commodity trading advice tailored to any particular client’s situation or investment objectives. Supporting documentation for any claims (including claims made on behalf of options programs), comparisons, statistics, or other technical data, if applicable, will be supplied upon request. tastylive is not a licensed financial adviser, registered investment adviser, or a registered broker-dealer.  Options, futures, and futures options are not suitable for all investors.  Prior to trading securities, options, futures, or futures options, please read the applicable risk disclosures, including, but not limited to, the Characteristics and Risks of Standardized Options Disclosure and the Futures and Exchange-Traded Options Risk Disclosure found on tastytrade.com/disclosures.

tastytrade, Inc. ("tastytrade”) is a registered broker-dealer and member of FINRA, NFA, and SIPC. tastytrade was previously known as tastyworks, Inc. (“tastyworks”). tastytrade offers self-directed brokerage accounts to its customers. tastytrade does not give financial or trading advice, nor does it make investment recommendations. You alone are responsible for making your investment and trading decisions and for evaluating the merits and risks associated with the use of tastytrade’s systems, services or products. tastytrade is a wholly-owned subsidiary of tastylive, Inc.

tastytrade has entered into a Marketing Agreement with tastylive (“Marketing Agent”) whereby tastytrade pays compensation to Marketing Agent to recommend tastytrade’s brokerage services. The existence of this Marketing Agreement should not be deemed as an endorsement or recommendation of Marketing Agent by tastytrade. tastytrade and Marketing Agent are separate entities with their own products and services. tastylive is the parent company of tastytrade.

tastycrypto is provided solely by tasty Software Solutions, LLC. tasty Software Solutions, LLC is a separate but affiliate company of tastylive, Inc. Neither tastylive nor any of its affiliates are responsible for the products or services provided by tasty Software Solutions, LLC. Cryptocurrency trading is not suitable for all investors due to the number of risks involved. The value of any cryptocurrency, including digital assets pegged to fiat currency, commodities, or any other asset, may go to zero.

© copyright 2013 - 2024 tastylive, Inc. All Rights Reserved.  Applicable portions of the Terms of Use on tastylive.com apply.  Reproduction, adaptation, distribution, public display, exhibition for profit, or storage in any electronic storage media in whole or in part is prohibited under penalty of law, provided that you may download tastylive’s podcasts as necessary to view for personal use. tastylive was previously known as tastytrade, Inc. tastylive is a trademark/servicemark owned by tastylive, Inc.