Build a Better Process

# Autocorrelation Definition and Quiz

The name scares people off but the concept can be easy to grasp, and has many uses.
1. Define - Define Autocorrelation for portfolio risk and alpha models.
2. Context - Use Autocorrelation in a sentence.
3. Quiz - Test yourself.
Updated: February 16, 2021
Here we have a measure that helps to evaluate the success of investment models over time, see how below.

/ factorpad.com / fin / glossary / autocorrelation.html

## Autocorrelation definition

Autocorrelation, or serial correlation, is the correlation of one variable with itself over different time periods. This is important for testing whether stock returns behave like independent variables, which is an assumption of statistical tests of several important theories, including the Efficient Market Hypothesis (EMH).

To calculate autocorrelation for monthly returns with a 1-month lag, use nearly the same return stream except stagger the y-variable dependent variable by 1 month. In a basic 36-month example, the x-variable in the regression could go from Jan 2014-Dec 2016 and the y-variable would then go from Feb 2014-Jan 2017.

Synonym: serial correlation, cross correlation

For context, imagine running an autocorrelation of risk measures. Here, historically, statistically significant autocorrelation has been observed. A likely reason is that volatile periods in financial markets are often followed by other volatile periods. Some refer to this as a 'volatility cluster'.

With respect to correlations of stock returns, some use autocorrelation studies to determine the level of decay in alpha signals and for research on stock momentum.

### In a Sentence

Bud:  Hey Guy, nice chart, eh? Solid uptrend, nice doji, MACD, and strong momentum.
Guy:  You are the Technician, but technically, it looks like autocorrelation to me.

### Video

Many terms have 4-5 minute videos showing a derivation and explanation. If this term had one, it would appear here.

Videos can also be accessed from our YouTube Channel.

### Video Script

If this term had a video, the script would be here.

### Quiz

A possible economic justification for positive autocorrelation could be the tendency for investors to sell winners. | True or False?

False, performance chasing could result in positive autocorrelation.

Commercial risk model providers often adjust their models for the fact that volatility demonstrates positive autocorrelation. | True or False?

True.

Still unclear on Autocorrelation? Check out our 27-video deep-dive in Excel in the Quant 101 Series.

### Related Terms

Our trained humans found other terms in the category statistics for finance you may find helpful.

## What's Next?

Subscribe on YouTube so you catch the latest video. Email list too.

• For all terms in the Glossary, click Outline.
• To review when to use Arithmetic Returns hit Back.
• Feeling tipsy? Support your remote tutorial maker, click Tip.
• To learn about Behavioral Finance, click Next.

/ factorpad.com / fin / glossary / autocorrelation.html

investment autocorrelation
autocorrelation of stock returns
serial correlation of investments
cross correlation of stocks
single variable correlation over multiple time periods
regression of stock returns
decay in alpha signal
stock momentum and autocorrelation
efficient market hypothesis
high risk is correlated with high risk
assumption to efficient market hypothesis
statistical test of stock performance
stock volatility clusters

A newly-updated free resource. Connect and refer a friend today.