Stratification is a statistical technique of breaking down value/data into meaningful categories or classifications.
This is considered one of the basic 7 QC Tools and is extensively used in Problem Solving Techniques such as 8D, PDCA, and Six Sigma.
Table of Contents
Stratification Definition and Meaning
Stratification is a technique or method that can be defined in many ways:
A technique used to analyze and divide a universe of data into homogeneous groups called -Strata.
It involves observing data, splitting them into distinct classes or categories to see a different process for better analysis.
In Stratification, data recording/observation carried out from multiple sources like shifts, machines, days, people, etc.
In other words, it is a method to divide the data into sub-categories and obtain meaningful information to solve a quality problem.
A statistical technique or system of formation of layers or classes or categories to analyze the problem.
Example: Machine wise Stratification.
Rejection data collected from three different machines and date wise trend chart plotted. From the chart, we can see that machine-3 is contributing to high defects/rejection as compare to machine-1. Therefore, the main focus area/source is a machine no. 3 for necessary measures to reduce process variation and rejection level.
When to use Stratification?
- When the data come from different sources or conditions, such as data collected from different shifts, machines, people, days, suppliers and population groups, etc.
- Used extensively to control and improve the process. Is the process running OK and how long?
How it is carried out ?
It is carried out by splitting process data into distinct layers or sub-groups and understand the different meaningful patterns to analyze and solve problems.
Benefits of Stratification
- Overall improve in product and process quality.
- Unknown strands of data can be identified.
- Systematic reduction of Process Variation-common cause of variation.
Example:
Stratification helps in analysing “Quality Cost”.
- Internal Failure cost
- External Failure cost
- Prevention cost
- Appraisal cost
See also
- 7 QC Tools | Seven Basic Quality Tools of Problem Solving and Process Quality Improvement.
- TQM | TOTAL QUALITY MANAGEMENT | TQM Meaning
- What is Scatter Diagram? Correlation Chart | Scatter graph | Types and Benefits
