Six Sigma Tool Navigator: The Master Guide for Teams

2017-07-07 02:10:07

AKA

Multiple Line Graph

Classification

Analyzing/Trending (AT)

Tool description

The stratification method stratifies (separates) an existing set of data into sub-groups to determine what effect each subgroup of data has on an abnormal pattern or condition. Stratification helps in isolating and unmasking the real cause of a problem.

Typical application

To isolate abnormalities among data sets.

To break down and analyze abnormal distributions.

To verify the effects of subgroups to identify casue(s).

To identify root causes of total variation.

To analyze data to discover improvement opportunities.

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

links to other tools

before

Line Chart

Frequency Distribution (FD)

Data Collection Strategy

Checksheet

Observation

after

Variance Analysis

Problem Specification

Potential Problem Analysis (PPA)

Trend Analysis

Stratum Chart

Notes and key points

Encode and designate all subgroups plotted. Preferably add the "total group" graph for instant comparisons. Apply the 3:4 ratio graph construction rule.

Step-by-step procedure

STEP 1 Collect and verify data to be plotted. See example Shipping Errors over 8 Weeks.

	Wk1	2	3	4	5	6	7	8

Company Total:	40	32	30	34	41	29	39	27
Workshift A	28	20	21	19	33	18	22	18
Workshift B	8	7	4	8	3	6	10	4
Workshift C	4	5	5	7	5	5	7	5

STEP 2 Construct a stratification chart. The height of the vertical axis should be 75 percent of the length (100 percent) of the horizontal axis (3:4 ratio rule).

STEP 3 Plot the data using the error totals for 8 weeks of all 3 workshifts. Also plot the company totals.

STEP 4 Encode plotted data, designate lines, and label axes. Date the stratification chart.