Kurtosis: Definition, Types & Example

Kurtosis is a statistical measure that describes the tailedness or sharpness of the peak in a data distribution.

Table of Contents

What Is Kurtosis?

Kurtosis is a statistical term that describes how significantly the tails of a distribution deviate from the tails of a normal distribution. In other words, kurtosis determines whether the tails of a given distribution have extreme values.
 
Mathematically, kurtosis is calculated using the fourth central moment of a distribution. The formula is:

Types of Kurtosis

Kurtosis is classified into three main types:

1. Mesokurtic (Normal Distribution)

A mesokurtic distribution has a kurtosis of 3 (or zero when excess kurtosis is used). This indicates a moderate peak and normal tail distribution, similar to a standard normal curve.

Example:
The height of adult males in a population often follows a mesokurtic distribution.

2. Leptokurtic (High Kurtosis)

A leptokurtic distribution has kurtosis greater than 3. It has a higher peak and fatter tails, meaning that extreme values (outliers) occur more frequently than in a normal distribution.

 

Example:

Stock market returns are often leptokurtic because financial data tends to have extreme fluctuations.

3. Platykurtic (Low Kurtosis)

A platykurtic distribution has kurtosis less than 3. It has a flatter peak and thinner tails, indicating that data is more evenly spread with fewer outliers.


Example:

Uniform distributions, such as rolling a fair die multiple times, tend to be platykurtic.

Why Kutosis Is Important?

Kurtosis plays a significant role in various fields, helping analysts understand the distribution of data and its implications.

In finance, kurtosis is crucial for risk assessment, as it helps identify the likelihood of extreme gains or losses. Investors and risk analysts closely examine the kurtosis of stock returns to determine how often large price swings occur.

Leptokurtic distributions, which exhibit frequent extreme values, indicate highly volatile assets that can experience sudden spikes or crashes.

On the other hand, mesokurtic distributions represent moderate volatility, with stock prices following a more predictable pattern.

Meanwhile, platykurtic distributions signify stability, with fewer extreme fluctuations, making them characteristic of low-risk assets like government bonds.

The Bottom Line

Kurtosis is an essential statistical measure that provides insights into the shape of a data distribution. By understanding its types—mesokurtic, leptokurtic, and platykurtic—we can better interpret data and make informed decisions in various fields.

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