Seven Basic Quality Control Tools and Techniques | Quality Control

Seven Basic Quality Control Tools and Techniques |
Quality Control

  •      Run Charts
  •      Pareto Charts
  •      Flow Charts
  •      Scatter Diagrams
  •      Cause and Effect
  •      Control Charts

1) Histograms

A Histogram is a bar graph used to present frequency
data. Histograms provide an easy way to evaluate the
distribution of data over different categories

Steps in making Histogram

  1. Define Categories for Data
  2. Collect Data, sort them into the categories
  3. Count the Data for each category
  4. Draw the Diagram. Each category finds its place on the
  5. The bars will be as high as the value for the

Histogram-Seven Basic Quality Control Tools and Techniques

       Fig. Histogram

The histogram reveals the following about the

  • Centering of the process
     The centering of the data provides
    information on the process about some mean.

  • Spread of the
     Histogram width defines the
    variability of the process about the mean

  • Shape of the
    Bell or normal shaped
    histogram is expected. Other than normal or bell shape
    means something wrong with the process responsible for poor

Limitations of the Histograms 

  • The randomness in the data in developing histogram
    losses the vital information
  • As data are not represented in order, the
    time-dependent or time-related trends in the process may not
    be revealed.

2) Run Chart

Run Charts are better option over histograms as they
overcome the limitations of the histograms. A run chart
represents change in measurement over a sequence or time. Run
charts are used to determine cyclic events and their average

Steps in making Run Charts

  • Arrange data with time sequence
  • Plot the data in order
  • Interpreting Data
run charts
Fig. Run Chart

The run chart reveals the following about the

  • Run charts display process performance over

  • Trends, cycles, and large variations are clearly

  • An average line may be added to a run chart to
    clarify movement of the data away from the process

3) Pareto Chart

VILFREDO PARETO an Italian economist provided a golden
rule which fits into many managerial situations. The golden
Pareto principle : “The majority of wealth is held by a
disproportionately small segment of the population”. This
principle is also known as 80 / 20 principle. 80% of the
problems are caused by 20% of the causes

JURAN has noticed that this principle applies to
quality improvement as well. According to Juran the problems
that occur a few are very frequent while other important
problems occur seldom. He given the phrase as “Vital few and
the trivial many”

Pareto Charts are used to apply the 80/20 rule of
Joseph Juran which states that 80% of the problems are the
result of 20% of the problems. A Pareto Chart can be used to
identify that 20% root causes of problem.

A Perot chart is similar like

Steps in making Pareto Charts

  • First define categories
  • Sort the data into the Categories and find out the
  • frequency of occurrence of each category
  • Arrange the categories in descending order
Pareto Charts
Fig.  Pareto

4) Flow

A flow chart is way of representing a procedure
using simple symbols and arrows. A Flow chart shows the
activities in a process and the relationships between them. A
Flow chart lets a process be understood easily. It also
demonstrate the relationships between the elements of the

Flow chart
Fig. Flow chart

Steps in making Flow Charts

  • Determine the Process need to be represented by flow
  • List down the sequence of operation and other
  • Start at a certain point and go then step by
  • Using flow chart symbols
  • Write the titles to each element

5) Scatter Diagram

Scatter diagram is a statistical chart which shows
a trend in a series of data. It demonstrates correlations
between values.

Scatter Diagram
Fig. Scatter Diagram

Steps in making Scatter Diagram

  1. Plot the data points
  2. Draw trend line by fitting a straight line
  3. Upward line shows the positive trend(X increases and Y
  4. Downward line shows the negative trend  (X increases
    and Y decreases)

6) Cause and Effect Diagrams.

A Cause and Effect Diagram shows the relationship
between effect and the categories of their causes. The
diagram look like a fishbone it is therefore also called
fish-bone diagram. Cause and effect diagram enables a team to
focus on the content of a problem. It helps to provide a
comprehensive picture of the problem and the root causes of
the same.

Cause and Effect Diagram
Fig. Cause and Effect Diagram

Steps in making Cause and
Effect Diagram

  • Determine the Effect or Problem
  • Categorize the possible causes
  • Describe the possible causes

7) Control Chart

Control charts are statistical tool, showing whether a
process is in control or not.  It is a graphical tool
for monitoring the activities of an ongoing process also
referred as Shewhart control charts.

 Control Chart
Fig. Control Chart

Steps in making control chart

  • Define Upper limit, lower limit and Center
  • Draw Chart
  • Plot the data points into chart
  • Interpret the control chart