Ishikawa's Seven Basic Tools of Quality Control

Ishikawa's Seven Basic Tools of Quality Control

1. Cause and Effect Diagrams

   • Identify underlying symptoms
     • Find the root cause
   • Causes identified
     • Brainstorm
       • Working Backwards

2. Control or Shewhart Charts

   • Manufacturing or business process
     • Statistical control or not?
       • Stable
         • Data used to predict future performance
       • Not in control
         • Data helps to find sources of variation
   • Allows significant change to be differentiated from natural process
   • Objective and discipline approach

3. Check Sheet

   • Collects data in real time
   • Quick, easy and efficient recording
   • Clasificación, Location, Frecuency, Measurement Scale, Check List

4. Histogram

   • Visual Impression of data distribution
   • Used to plot density of data

5. Pareto Chart

   • Highlights most importan set of factors
   • Represents most common source of defects

6. Scatter plot or graph

   • Displays values for two variables
   • Used when a variables is under control of the experimenter
   • Suggests various kinds of correlations
     • Positive, negative or uncorrelated
   • Shows non linear relationships

7. Stratified Sampling

   • Sampling from population
   • Dividing members into homogenous subgroups
   • Strata
     • Mutually exclusive
     • Collectively exhaustive
     • Random or systematically sampling
       • Improves representativeness