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6Sigma Stats-Distribution Classes

published on March 31, 2014

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!

published on March 31, 2014


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