Tool 191: Stratum Chart

AKA

Surface Chart, Sarape Chart

Classification

Analyzing/Trending (AT)

Tool description

A stratum chart is an effective means to demonstrate cumulative additions of data that range from low to high and that are plotted along a horizontal time scale. Coloring or shading is used to differentiate among variables and to provide a quick interpretation of accumulation and relationships between plotted data.

Typical application

• To show cumulative changes in data over time.

• To display the effect of plotted variables, each variables' gradual change over time and relationships to each other.

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
2	Engineering
	Project management
3	Manufacturing
	Marketing/sales
	Administration/documentation
4	Servicing/support
	Customer/quality metrics
	Change management

links to other tools

before

• Data Collection Strategy

• Checksheet

• Frequency Distribution (FD)

• Trend Analysis

• Sampling Methods

after

• Major Program Status

• Process Analysis

• Monthly Assessment Schedule

• Information Needs Analysis

• Presentation

Notes and key points

• Lines or curves cannot overlap.

• Coloring or shading is needed to demonstrate the effect of cumulative changes in data plotted.

Step-by-step procedure

• STEP 1 Collect historical data for variable to be plotted. See example TQM-Related Start-up Costs.

• STEP 2 Scale the stratum chart to allow for highest cumulative number.

• STEP 3 Plot the data along the horizontal time scale as shown in the example.

• STEP 4 Color or provide pattern shading for variable data plotted.

• STEP 5 Check the stratum chart for accuracy and provide date of issue.

Example of tool application