Six Sigma is a methodology used to improve quality management within a company. It utilizes process and statistical analysis to improve the company's processes and performance across different parts of the value chain. It provides a structured and disciplined way for the company to consistently produce quality products or services. Defect rates decrease as Six Sigma levels increase. The goal of creating so-called lean processes via Six Sigma is to eliminate excessive delays, production, inventory, process inefficiencies, transportation and effort. This is done by creating detailed process diagrams and brainstorming on ways to make each step in the process better. Six Sigma uses statistical measures such as variance to evaluate data.

Gather data sets for analysis. As an example, you can tabulate the number of defects on a production line per hour over a specific period of time. You can also tabulate the number of customer returns per day over a period of time.

Calculate the mean or average of the data set by adding all the data values and dividing that value by the total number of data values.

Calculate the difference between each value in the data set and the mean. Add all of these differences together. Divide the final sum by the total number of values in the data set to get the value for the variance.

Evaluate the variance for different variables regularly as you implement Six Sigma processes.