4, is a diagram that plots data points
allowing trends to be observed between one variable and another. The scatter diagram
is used to test for possible cause-and-effect relationships. A danger is that a
scatter diagram does not prove the cause-and-effect relationship.
y = 1.9553x + 1.9065
R2 = 0.963
1
6
11
16
21
26
0.1 1.1 2.1 3.1 4.1 5.1 6.1 7.1 8.1 9.1 10.1
Number of Review Hours
Number of Defects
Figure 18.4 Scatter diagram.
0 2 4 6 8
10
12
14
16
18
20
Requirements
Design
Timing
Hardware
Logic
Interface
Security
Data
Type or Source of Defect
Number of Defects
Figure 18.3 Pareto chart.
Statistical Process Control n 241
Cause and Effect/Fishbone Diagram
The cause and effect or fishbone diagram, shown in Figure 18.5, is a graphical
display of problems and causes. This is a good way to capture team input from a
brainstorming meeting, from a set of defect data, or from a check sheet.
Control Chart
The control chart, shown in Figure 18.6, is basically, a run chart with upper and
lower limits that allows an organization to track process performance variation.
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