Quality and Reliability Methods - SAS

Chapter 10 Variability Charts 153
Variability Charts
Variability Charts
A variability chart is built to study how a measurement varies across categories. Along with the data, you can
view the mean, range, and standard deviation of the data in each category. The analysis options assume that
the primary interest is how the mean and variance change across the categories.
A variability chart has the response on the y-axis and a multilevel categorized x-axis. The body of the chart
can have the features illustrated in Figure 10.2.
Figure 10.2 Example of a Variability Chart
points with
range bars
group means
cell means
lines connecting
cell means
Launch the Variability Platform
Select Analyze > Quality and Process > Variability / Attribute Gauge Chart to show the Variability Chart
launch dialog shown in Figure 10.3. You specify the classification columns that group the measurements in
the X, Grouping list. If the factors form a nested hierarchy, specify the higher terms first. If it is a gauge
study, specify operator first and then the part. Specify the measurement column in the Y, Response list. If
you specify more than one Y column, there will be a separate variability chart for each response.
Specifying a standard or reference column that contains the “true” or known values for the measured part
enables the Bias and Linearity Study options. Both of these options perform analysis on the differences
between the observed measurement and the reference or standard value.
The following example uses 2 Factors Crossed.jmp, found in the Variability Data folder.