Kurtosis
Shape of the Distribution

There are three types of kurtosis which is a description of the "peakedness" or "flatness" of the probability distribution curve relative to the bell curve of a normal distribution. This does not have to do with skewness.

1) Platykurtic - negative kurtosis value indicating a flatter distribution that normal bell curve. The lower the value the flatter the distribution with more spread. An example is the Uniform Distribution which has a kurtosis = -1.2.

2) Leptokurtic - positive kurtosis value indicating a peaked shaped distribution compared to normal bell curve. The higher the value the sharper the peak the distribution and less spread. An example is the Double Exponential Distribution which has a kurtosis = 3.

3) Mesokurtic - when kurtosis value = 0. A normal distribution has a kurtosis value of zero. It is in between the first two types.


Calculating the Kurtosis value

The formula for calculating kurtosis is shown below with an example. The sample size must be a least four. 

s = sample standard deviation

n = number of samples



Examples

There are two sets of data shown with 15 samples each. The calculations are shown with the kurtosis value for each set. The formula in Excel is shown in the upper right.



Other examples

Platykurtic 

Leptokurtic



Return to BASIC STATISTICS

Return to the ANALYZE phase

Templates and Calculators

Return to the Six-Sigma-Material Home page

Custom Search


Site Membership
LEARN MORE


Six Sigma

Templates, Tables & Calculators


Six Sigma Slides

CLICK HERE

Green Belt Program (1,000+ Slides)

Basic Statistics

Cost of Quality

SPC

Process Mapping

Capability Studies

MSA

SIPOC

Cause & Effect Matrix

FMEA

Multivariate Analysis

Central Limit Theorem

Confidence Intervals

Hypothesis Testing

T Tests

1-Way ANOVA

Chi-Square

Correlation

Regression

Control Plan

Kaizen

MTBF and MTTR

Project Pitfalls

Error Proofing

Z Scores

OEE

Takt Time

Line Balancing

Yield Metrics

Sampling Methods

Data Classification

Practice Exam

... and more



Need a Gantt Chart?

Click here to get this template