Statistical Quality Control - Definition, Objectives & Tools

Fri, 04/24/2009 - 19:23 -- Umar Farooq

Statistical Quality Control Definition

Statistical Quality Control SQC developed in the United States in 1930-40 by W.A Shewhart, and used for decades in American and Japanese companies.  The basic approach consist the following steps;

  1. Awareness that a problem exists
  2. Determine the specific problem to be solved
  3. Diagnose the causes of the problem
  4. Determine and implement remedies to solve the problem
  5. Implement controls to hold the gains achieved by solving the problem

Statistical Quality Control is one of the most known and popular in the several process control methods.  This technique is used to:

  • Analyze a work process or its outputs
  • Identify variations through date
  • Take appropriate action in order to achieve statistical control
  • Improve the capacity of the process

Statistical Process Control (misleading)

The term statistical process control sometimes misleading, many people use it frequently to manufacturing process whereas

  • Useful for improving results in other non-manufacturing areas  (Sales & Staff)
  • Can be used in many of the activities and functions o service industry
  • A systematic way of problem solving

A process is a set of steps, causes and conditions comprising activity that transforms inputs into outputs. (Airline industry: reservation, baggage, handling, loading passengers, meal service etc. The ratio of output to input is called productivity.

Objectives of Statistical Process Control are:

  • Increase the ratio of output to input
  • Reduced the variation in the output of the process

Tools for Statistical Quality Control

Every process depends on gathering and analysis of data what are profuse in any organization that is involved in the process problem. The basic tools are:

  • Data Collection
  • Data Display

Data Collection

A check sheet is useful in assembling and compiling data concerning a problem. It uses for data collection to view for any unwanted element. The functions of a check sheet are

  • Production process distribution checks
  • Defective item checks
  • Defect location checks
  • Defect cause checks
  • Checkup confirmation checks

Data Display

When a company collects data it is converted on to various types of charts and forms for the purpose of display and analysis of data.  Charts have different types as:

  • A bar graph  (present simple data and easy understood)
  • A scatter diagram (relationship between two types of data)
  • A histogram (distribution of data in term of frequency)
  • A Pareto diagram (statistical tool in problem analysis)