Distribution Fitting (Life Distribution)

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Use to model a single continuous variable with a probability distribution and estimate a variety of parameters (e.g., mean, percentiles, probabilities). This platform is designed to fit and compare many different distributions and can analyze data that is censored (incomplete). Note: Though frequently used to analyze time-to-event data, the analysis methods can be used to model any continous variable (e.g., force-to-event).

Distribution Fitting (Life Distribution)

1. From an open JMP^® data table, select Analyze > Reliability and Survival > Life Distribution.
2. Select a continuous time variable from Select Columns, then click Y, Time to Event (continuous variables have blue triangles).
3. If the data contain censored values, select the censoring variable and click Censor. Change the Censor Code if needed (the default is Censored).  
4. Select the Confidence Interval Method (the default is Wald), and click OK. JMP will display:

• An Event Plot (click on the gray icon to open), which graphically depicts failures (denoted by X’s) and censored events (denoted by triangles).
• The Compare Distributions panel, which allows you to compare the fit of various distributions.
• The Statistics panel, with summary statistics, parameter estimates and profilers for each distribution selected.

 To Compare Distributions:

• Click a radio button under Scale to apply the scale for a distribution. If the selected distribution fits the data well, the plotted points will approximate a straight line.
• Check a box under Compare Distributions to fit a distribution and display a fitted line, shaded confidence bands and a Profiler for the distribution.
• Select Fit All Distribution or Fit All Non-negative under the top red triangle to compare all distributions using model comparison criteria such as AIC and BIC.

Tips:

• To compare the same life distribution across groups, use the Compare Groups option in the Life Distribution dialog.  Other options, such as show survival curve and view tabbed report are available from the top red triangle.
• If studying competing failure causes, enter the variable in the Failure Cause field in the launch window.
• Continuous distributions can also be fit in Analyze > Distribution. 

Fan.jmp (Help > Sample Data Folder > Reliability)

Visit Reliability and Survival Methods > Life Distribution in JMP Help to learn more.