17.4. Piecewise Exponential Models
Statistical models can extend the analysis of grouped survival data by providing a description of the pattern of event rates. They can describe this pattern over time as well as describe the variation due to the influence of treatment and other explanatory variables. One particularly useful model is the piecewise exponential model.
Consider Table 17.7, which contains information pertaining to the experience of patients undergoing treatment for duodenal ulcers (based on Johnson and Koch 1978). One of two types of surgeries was randomly assigned: vagotomy and drainage or antrectomy, or vagotomy and hemigastrectomy. The patients were evaluated at 6 months, 24 months, and 60 months. Death and recurrence are considered ...
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