Quality and Reliability Methods - SAS

Chapter 14 Lifetime Distribution II 243
Navigating the Fit Life by X Report Window
Summary of Data
Scatterplot
The Summary of Data report gives the total number of observations, the number of uncensored values, and
the number of censored values (right, left, and interval).
The Scatterplot of the lifetime event versus the explanatory variable is shown at the top of the report
window. For the Devalt data, the Scatterplot shows Hours versus Temp. Table 14.1 indicates how each type
of failure is represented on the Scatterplot in the report window.
Table 14.1 Scatterplot Representation for Failure and Censored Observations
Event
failure
right-censoring
left-censoring
interval-censoring
Scatterplot Representation
dots
upward triangles
downward triangles
downward triangle on top of an upward triangle, connected by a solid line
Using Scatterplot Options
Density curves and quantile lines for each group can be specified by clicking on the red-triangle menu for
the scatterplot. You can select the Show Density Curves option to display the density curves. If the
Location or the Location and Scale model is fit, or if Nested Model Tests is checked in the launch
window, then the density curves for all of the given explanatory variable levels are shown. You can select the
Add Density Curve option, where you can specify the density curve that you want, one at a time, by
entering any value within the range of the accelerating factor.
After the curves have been created, the Show Density Curves option toggles the curves on and off the plot.
Similarly, you can specify which quantile lines you want by selecting Add Quantile Lines, where you enter
three quantiles of interest, at a time. You can add more quantiles by continually selecting the Add Quantile
Lines. Default quantile values are 0.1, 0.5, and 0.9. Invalid quantile values, like missing values, are ignored.
If desired, you can enter just one quantile value, leaving the other entries blank. Figure 14.4 shows the initial
scatterplot; Figure 14.5shows the resulting scatterplot with the Show Density Curves and Add Quantile
Lines options selected.
To swap the X and Y axes, select the Transpose Axes option.
The default view of the scatterplot incorporates the transformation scale. Turn off this option by selecting
Use Transformation Scale.