DMAIC: Measure Phase (cont.)

Halden Zimmermann – DMAIC: Measure Phase continued…

Halden Zimmermann


• Determines if the measurement system can adequately discriminate between different parts

• Identifies the source of the variation in measurements (i.e., operators, testing methods)

Control Charting or Statistical Process Control (SPC) Tool

Purpose: The concepts of Statistical Process Control (SPC) were initially developed by Dr. Walter Shewhart of Bell Laboratories in the 1920s and were expanded upon by Dr. W. Edwards Deming, who introduced SPC to Japanese industry after WWII. After early successful adoption by Japanese firms, Statistical Process Control has now been incorporated by organizations around the world as a primary tool to improve product quality by reducing process variation.

Dr. Shewhart identified two sources of process variation. Chance variation is inherent in process and stable over time, and Assignable or Uncontrolled variation is unstable over time. Assignable or Uncontrolled variation is the result of specific events outside the system. Dr. Deming relabeled chance variation as Common Cause variation and assignable variation as Special Cause variation. Based on the laws of statistics and probability, Dr. Shewhart and Dr. Deming devised control charts to plot data over time and identify both Common Cause variation and Special Cause variation.

A Control Chart is a specialized time series plot designed to identify abnormal patterns of variability in a process. The X-bar & R-charts are probably the most commonly used control charts.

Halden Zimmermann control chart example
Control Chart Example

Application: Use with time-ordered sample data to identify an important quality characteristic.


Control Charts can help answer questions such as:
• Is my process (machine/operator) stable?
• Is the process average in control?
• Does the process average remain consistent between subgroups?

•What is the variability in the manufacturing process?



2 thoughts on “DMAIC: Measure Phase (cont.)

  1. The DMAIC model is a model to standardize problem solving and improve the success rate for implementing and sustaining the project benefits… Of course this works well for larger projects, but how do you manage quick hits or get organized around just go do it type activity?

    Another question would be is it better to do projects at a high rate but only get you to an 80% solutions or using DMAIC to get to a 99% solution.

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