Life Testing Formula Builder

Choose Statistics __image\arrow5.gif Survival __image\arrow5.gif Life Testing. On the Model page of the dialog, select a data set and click the Create Formula button. The dialog shown below appears.

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Variable

Choose Variables Variables of the Data Set selected in the model page are displayed in the Choose Variables field. To select more than one variable, press the CTRL key. After selecting variables, assign the selection as response or predictors to complete the formula. If you want to do transformations on variables, click Transformation.

Add Terms

Choose one or more variables from the Choose Variables dropdown list and then click Main Effects, or Main+Interact. The appropriate main effect and/or interaction terms are added to the formula. Click Cluster, Strata, Offset, Frailty, Gamma Frailty, Spline, or Ridge to define terms. The appropriate term is added to the formula.

Survival Response

The fields necessary to define the survival response vary depending on the type of censoring for the problem at hand. The Time 2 and Origin for Hazard fields are only enabled for a counting process. Choose a time variable from the variable list (Survival Times or Start Time) and click on the Time 1 button. Similarly select a variable representing the Censoring Indicator (event). If appropriate, select a variable for Time 2 (Ending Time). After all required variables have been selected, click the Add Response button to place the survival response in the formula.

Remove Term

Check Remove Intercept if you don't want an intercept in the formula. When predictors are added to the formula, they are listed as options in the Term field. If you decide to delete some terms, select the term first then click Remove. The term is removed from the formula and the option list in Term.