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, Vilfredo Pareto (1848–1923) –J. M. Juran is credited with being the ﬁrst person to apply it to industrial problems
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.
Table 2.4 Data for Quality Improvement Program Month No. of Employees Trained (000) Cost of Training (000) January1223 February1019 March1027 April1120 May915 June610 July814 August58 September69 October35 November23 December24
Variations of Scatter Plots Use number or special symbols for duplicated data points. Use “range frames”, instead of scales
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 12345678 9 10 Sample number Upper control limit Central Line Lower control limit 11 11 22 22 =011 22 33 95% 99.73% -1 -2 -3
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 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.
2.8 The 7 Newer Tools Afﬁnity Diagram Interrelationship Digraph Tree Diagram Prioritization Matrix Matrix Diagram Process Decision Program Chart Activity Network Diagram
2.8.1 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 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 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.
2.8.4 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 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 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.