# “How-To” Articles

## Getting Your Primary Metric Right

Before any six sigma project can get off the ground successfully, there is one critical metric that must be identified, the primary metric. In the DMAIC process, the define stage allows ample opportunity to clearly identify what the project will impact. This leads to the assignment of establishing your primary metric. The primary metric is …

## How to Define a Process

The essential method for how to define a process is without question the process map. The process map helps you to understand a process and its component steps. Process maps help determine where and how a process begins and ends as well as all the steps and decisions in between. By learning the basics of …

## Normal Distribution and Normality

The normal distribution is also known as a Gaussian distribution. It is the most frequently referenced distribution and it approximates many natural tendencies of data. The normal distribution is a probability distribution of a continuous random variable whose values spread symmetrically around the mean. A normal distribution can be completely described by using its mean …

## How to Write a Project Charter

In a previous article we stated that DMAIC is a structured and rigorous methodology designed to be repeatedly applied to ANY process in order to achieve Six Sigma. We also stated that DMAIC was a methodology that refers to 5 phases of a project. Define Measure Analyze Improve Control Given that the premise of the DMAIC methodology …

## Rolled Throughput Yield

Rolled Throughput Yield (RTY) is a process performance measure that provides insight into the cumulative effects of an entire process. RTY measures the yield for each of several process steps and provides the probability that a unit will come through that process defect free. RTY allows us to expose the “hidden factory” by providing visibility …

## DPMO – Defects Per Million Opportunities

DPMO is one of a few important Six Sigma metrics that you should get comfortable with if you’re associated with Six Sigma. In order to understand DPMO it’s best if you first understand both the nomenclature and the minor nuances such as the difference between defect and defective. DPMO Nomenclature: Defects = D Unit = U Opportunity …

## Pareto Chart

The Pareto Principle is commonly known as the “law of the vital few” or “80:20 rule”. It means that the majority (approximately 80%) of effects are the result of only a few (approximately 20%) of the causes. This principle was first introduced in the early 1900s by Wilfried Fritz Pareto, an Italian economist who observed …

## Mood’s Median Test with SigmaXL

What is Mood’s Median Test? Mood’s median test is a statistical test to compare the medians of two or more populations. Null Hypothesis (H0): η1 = … = ηk Alternative Hypothesis (Ha): At least one of the medians is different from the others The symbol k is the number of groups of our interest and …

## Paired T Test

Hypothesis testing allows us to validate an assumption or a “hypothesized” conclusion. We are able to accomplish this by using data and statistical measures that give us a better understanding of the risks we are taking if we reject or fail to reject the null hypothesis. Using a Paired t Test is necessary when the …