This article was originally presented as a PowerPoint presentation by Matt Savage at the 2006 NAHQ conference.

For more articles and to learn more about how these charts were produced using CHARTrunner, please visit the PQ Systems Healthcare Quality page.

Introduction

• What are process improvement (PI) or control charts?
• Which process improvement chart is the pick of the litter?
• Which process improvement charts are full of fleas?
• The recommended approach.

Types of PI or control charts

Measurement control charts:

• Individuals and Moving Range (X-Mr chart)
• X-Bar & Range chart
• X-Bar & Sigma chart
• Others: Median, Cusum, Moving Average

Attributes control charts:

• Nonconforming items (p-chart, np-chart)
• Nonconformities per subgroup (c-chart, u-chart)

Purpose of a control chart

Minimize the chance of making two types of mistakes.

• Overcontrol
• Undercontrol

Help you decide when to react and when not to react.

• Special cause variation
• Common cause variation

Chart selection flow chart

Benefits of attributes charts

• Easy to understand data in percent form
• Percent of _____ measure is common
• Ratios are commonly used – per 1,000 patient days
• Puts data in perspective
• c-charts are easy to create and use

Common problems with p-charts

• Large samples (denominator)
• Small samples
• Rare events
• Understanding of control limits
• Detecting sample-to-sample variation
• Plotting positive vs. negative occurrences & effect on control limits

Chart images

Click below to view image:

• Large denominator
• Small samples
• Rare events
• Understanding of control limits
• p-chart: Where do you start?
• Is this process in control?
• Sample-to-sample variation
• Plotting negative occurrences
• Plotting positive occurrences

Recommended approach

• Continue to present data in percentage form
• Consider a Dashboard chart for a snapshot
• Consider a Run chart for basic audience
• Consider an Individuals (X) chart
• Migrate toward an Individuals chart and Moving Range chart (X-Mr)

Learn more about CHARTrunner, the program used to produce the following charts.

Basic run chart	Individuals chart
Individuals & moving range chart	Individuals & moving range with Nelson rules
Summary p-chart	Summary individuals & moving range