Chapter 2 basic tools for improving quality
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Chapter 2 Basic Tools for Improving Quality. 7 Basic Tools by Ishikawa. Histogram Pareto chart Scatter plot Control chart Cheek sheet Cause-and-effect diagram Defect concentration diagram. 2.1 Histogram.

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Chapter 2 basic tools for improving quality

Chapter 2Basic Tools for Improving Quality

7 basic tools by ishikawa
7 Basic Tools by Ishikawa

  • Histogram

  • Pareto chart

  • Scatter plot

  • Control chart

  • Cheek sheet

  • Cause-and-effect diagram

  • Defect concentration diagram

2 1 histogram
2.1 Histogram

  • A histogram is a bar chart that shows the relative frequencies of observations in each of several classes.

  • Rule for determining the number of classes:

    • “Power of 2 rule”: for n observations, we would use a classes, where 2a-1 < n < 2a

    • Roundup a = lnn / ln 2 (=ROUNDUP(LN(100)/LN(2), 0)

    • a ~

2 2 pareto charts
2.2 Pareto Charts

  • A Pareto chart is a bar graph that shows the relative frequencies of observations in a descending order.

    • draws its name from an Italian economist, VilfredoPareto (1848–1923)

    • J. M. Juran is credited with being the first person to apply it to industrial problems

2 3 scatter plots
2.3 Scatter Plots

  • A scatter plot is another simple graphical device

  • The simplest type is a bivariate scatter plot, in which two quantities are plotted.

  • Scaling of the two axes is somewhat arbitrary

  • A time sequence plot is a type of scatter plot in that data on one variable are plotted against a second variable, time.

  • A probability plot is another type of scatter plot.

Variations of scatter plots
Variations of Scatter Plots

  • Use number or special symbols for duplicated data points.

  • Use “range frames”, instead of scales

2 4 control charts
2.4 Control Charts

  • A control chart is a time sequence plot with “decision lines” added.

  • These decision lines are used to try to determine whether or not a process is in control.

    • Type I and II errors

Typical control chart











Typical Control Chart






















Sample number

2 5 check sheet
2.5 Check Sheet

  • A check sheet is a means of recording historical data on causes of nonconformities or nonconforming units.

    • The general idea is to record all pertinent information relative to nonconformities and nonconforming units, so that the sheets can facilitate process improvement.

    • Such information might include notes on raw materials, machine performance, or operator changes.

2 6 cause and effect diagram
2.6 Cause-and-Effect Diagram

  • The cause-and-effect diagram was introduced in Japan in 1943 by Professor Kaoru Ishikawa of the University of Tokyo.

    • For that reason it is sometimes called an Ishikawa diagram; it has also been called a fishbone chart.

2 7 defect concentration diagram
2.7 Defect Concentration Diagram

  • It is simply a schematic diagram that shows the various sides of a unit of production, with the positions where nonconformities occur pinpointed.

2 8 the 7 newer tools
2.8 The 7 Newer Tools

  • Affinity Diagram

  • Interrelationship Digraph

  • Tree Diagram

  • Prioritization Matrix

  • Matrix Diagram

  • Process Decision Program Chart

  • Activity Network Diagram

2 8 1 af nity diagram
2.8.1 Affinity Diagram

  • An affinity diagram is a set of ideas about a particular topic that are grouped into clusters.

  • The diagram is the end product of brainstorming that is performed in a prescribed manner.

2 8 2 interrelationship digraph
2.8.2 Interrelationship Digraph

  • An interrelationship digraph is used for identifying and exploring causal relationships between related ideas.

  • This is a step beyond an affinity diagram, as an interrelationship digraph is a figure with arrows indicating relationships between ideas.

2 8 3 tree diagram
2.8.3 Tree Diagram

  • A tree diagram is somewhat similar to a cause-and-effect diagram in that a desired effect (e.g., reducing delivery delays) can be shown pictorially as related to the factors that can lead to the effect.

  • A tree diagram will generally more closely resemble a company organizational chart in appearance than a cause-and-effect diagram.

  • A tree diagram is a more structured display than either an affinity diagram or an interrelationship digraph.

2 8 3 tree diagram1
2.8.3 Tree Diagram

2 8 4 prioritization matrix
2.8.4 Prioritization Matrix

  • A prioritization matrix is a relative ranking of issues jobs, objectives, products, and so on.

  • The ranking is accomplished by comparing the components pairwise so that a logical and consistent ranking results.

2 8 5 matrix diagram
2.8.5 Matrix Diagram

  • A matrix diagram is used for showing relationships between two or more sets of ideas, projects, and so on.

  • The matrix can have one of several different forms.

  • At least five forms have been used:

    • C-shaped

    • L-shaped

    • T-shaped

    • X-shaped, and

    • Y-shaped

2 8 6 process decision program chart
2.8.6 Process Decision Program Chart

  • A process decision program chart is a listing of undesirable events and corresponding contingency actions relative to planned actions.

  • It is used when there is considerable concern about the possibility of negative unanticipated outcomes.

2 8 7 activity network diagram
2.8.7 Activity Network Diagram

  • This is essentially a combination of two well-known techniques: PERT (Program Evaluation and Review) and CPM (Critical Path Method).