WinSPC.comWinSPC.com
Global leaders in real-time SPC software solutions
  • Software
    • WinSPC
      • WinSPC
      • Capture Data
      • Monitoring & Alarming
      • Analysis & Reporting
      • Industries Using WinSPC
      • How to Buy WinSPC
      • Supply Chain Quality
      • Achieve Regulatory Compliance
      • WinSPC System Requirements
      • Gauge Interface Hardware
      • Download WinSPC Trial
    • WinSPC Cloud
      • WinSPC Cloud
      • Retain Local System Flexibility
      • Gain These Cloud Benefits
      • Go Beyond Traditional SaaS
      • Data Protection & Security
    • WinSPC Envision
      • WinSPC Envision
      • Visibility
      • Mobility
      • Interactivity
      • How to Buy WinSPC Envision
      • Envision System Requirements
    • What is SPC?
      • What is SPC
      • SPC Training Materials
      • SPC Tools
      • SPC FAQ
      • SPC Glossary
  • Services
    • Implementation Assistance
    • System Integration
    • Customer-Specific Solutions
    • Software Validation
    • SPC & Software Training
      • SPC & WinSPC Courses
      • Course Delivery Options
      • Directions & Lodging
  • Resources
    • Contact Us & Support
    • Activate WinSPC Licenses
    • Customer Downloads (PRIV)
    • WinSPC Knowledgebase
    • Choosing WinSPC (BLOG)
    • DataNet News (News BLOG)
    • Ask The Expert (Tech BLOG)
    • DataNet Facebook Wall
    • DataNet Twitter Wall
Home » Ask The Expert » Can control charts detect small process shifts?

Can control charts detect small process shifts?

EWMA or Cusum charts are the best charts for detecting process shifts less than 1σ.

Typical control charts, such as Xbar & R and X & Mr, indicate whether or not a process is statistically stable. They detect process changes greater than 1.5σ and, because of this, are not the best tool to detect small process shifts. To detect small shifts, defined as shifts less than 1σ, use the EWMA or Cusum charts.

EWMA (Exponential Weighted Moving Average) chart weights moving average values according to time. The more recent the value, the greater the weight assigned to that value and, in effect, the greater the emphasis given to that value.

The Cusum (Cumulative Sum) chart plots the cumulative sum of deviations from a target value. These charts detect shifts from the process mean as small as 0.5σ. Cusum charts are plotted in 2 forms – V-Mask and Tabular Cusum (available in WinSPC).

Although EWMA and Cusum charts are very valuable in monitoring continuous processes where small changes have significant effects, it is not recommended that they be used as process improvement tools. Rather, process improvement decisions should be made using other tools such as control, pre-control and Pareto charts.

 

Steven Wachs, Principal Statistician
Integral Concepts, Inc.

Integral Concepts provides consulting services and training in the application of quantitative methods to understand, predict, and optimize product designs, manufacturing operations, and product reliability. www.integral-concepts.com


Download the white paper on how to jump-start a “mini” Six Sigma Quality program on a budget

April 25, 2019 Administrator WinSPC

Leave a Reply Cancel reply

You must be logged in to post a comment

Search WinSPC.com

Evaluate WinSPC

  • Quick Video Tour
  • Talk to an Expert
  • Download Trial
  • Request a Quote
  • Plan an Online Demo

Follow Us On

Follow Us On FacebookFollow Us On LinkedInFollow Us On TwitterFollow Us On YouTube

Find it on WinSPC.com

Follow Us on

Follow Us on FacebookFollow Us on LinkedInFollow Us on TwitterFollow Us on YouTube

Contact Us

866-4WINSPC

248-357-2200

248-357-4933

info*dqs.com

Southfield

Michigan USA

my_location Find Us - Map

Helpful Links

  • Knowledgebase Site
  • Ask The Expert – BLOG
  • What is SPC?
  • SPC Tools
  • SPC FAQ
  • SPC Glossary
  • Docs & Downloads

About Us

  • About DataNet
  • Find A Reseller
  • Contact Us & Support
  • Industries Using WinSPC
  • Customers Using WinSPC
  • DataNet News
  • DataNet Facebook Wall
  • DataNet Twitter Wall
  • Job Postings
DataNet Quality Systems - 29200 Northwestern Hwy - Southfield, MI 48034 -- Copyright © 1995-2021 -- All Rights Reserved