As we continue our journey in Six Sigma it seems pertinent to discuss the different types of distributions you will see in your analysis. Let’s start with one at a time. The most common distribution is the Normal Distribution and here’s what you should know about it.

First, what is a distribution?

Simply put, a distribution will tell you how often a variable occurs in your process. This is important because the commonness of your variables will inevitable create a foundation for your improvement project.

Types of Distribution

The Normal Distribution

A normal distribution (Gaussian Curve, the average person knows it as the Bell Curve) shows a equal distribution. The mean (the average) divides the data in half, 50% on the data on each side of the mean. The Normal Distribution will have the following hallmarks:

This distribution is considered to be the most important distribution.

The area under the curve should equal 1.

Physical aspects of the curve should resemble a hill and should be symmetrical.

Both directions on either side of the mean extend indefinitely and never touch the horizontal axis.

White noise in your process should produce a normal curve shape

The Z distribution has a mean of 0 and a standard deviation of 1.

The mean (average), median (mid-point) and the mode (most common value) should be the same data value.

Next week, it’s on to non-normal classifications.  Get to analyzing and if you need any help, reach out and let us know!