Tool 175: Scatter Diagram

AKA

Scatter Analysis, Scatterplot

Classification

Analyzing/Trending (AT)

Tool description

The scatter diagram is an analysis tool that plots related pairs of variables (factors) to display a pattern of relationship or correlation. This tool is extremely useful in detecting possible causes of a problem, the strength of the relationship, and how the change of one variable can affect the other.

Typical application

• To determine if a relationship exists between two sets of data.

• To demonstrate that a change in one activity or condition will affect the other.

• To verify a possible cause to an observed effect.

• To illustrate process improvement.

Problem-solving phase

	Select and define problem or opportunity
→	Identify and analyze causes or potential change
	Develop and plan possible solutions or change
→	Implement and evaluate solution or change
→	Measure and report solution or change results
	Recognize and reward team efforts

Typically used by

1	Research/statistics
	Creativity/innovation
	Engineering
	Project management
3	Manufacturing
5	Marketing/sales
	Administration/documentation
4	Servicing/support
2	Customer/quality metrics
6	Change management

links to other tools

before

• Checksheet

• Data Collection Strategy

• Events Log

• Defect Map

• Cause and Effect Diagram (CED)

after

• Presentation

• Information Needs Analysis

• Trend Analysis

• Potential Problem Analysis (PPA)

• Cost of Quality

Notes and key points

• Scatter patterns of correlation:

  

Step-by-step procedure

• STEP 1 Select two sets of data (variables) for plotting. See example Errors Made in Document Processing.

• STEP 2 Sort or rank the data pairs from low to high for both data sets.

• STEP 3 Construct a diagram and scale both axes in accordance with observed data pairs, from low numbers to high numbers of occurrence. For example, the X axis reflects a scale from 0 to 140 documents processed per day, the Y axis shows a scale from 0 to 25 errors made per day.

• STEP 4 Plot related data pairs on the grid—the diagram. Be careful in measuring the exact location of the intersecting point.

• STEP 5 Label and date the scatter diagram.

Example of tool application