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Complex Samples Cox Regression
Log-Minus-Log Plot
Figure 22-53
Log-minus-log plot
This plot displays the log-minus-log of the survival function, ln(−ln(suvival)), versus the survival
time. This particular plot displays a separate curve for each category of History of myocardial
infarction,withHistoryof ischemic stroke fixed at One and History of hemorrhagic stroke fixed at
None, and is a useful visualizationof the effect of History of myocardial infarction on the survival
function. As seen in the parameter estimates table, it appears that the survival for patients with
one or no priormi’s is distinguishable from the survival for patients with two prior mi’s, which in
turn is distinguishable from the survivalfor patients with three prior mi’s.
Summary
You ha vefit a Cox regression model for post-stroke survival that estimates the effects of the
changing post-stroke patient history. This is just a beginning, as researchers would undoubtedly
want to include other potential predictors in the model. Moreover, in further analysis of this
dataset you might considermore significant changes to the model structure. For example, the
current model assumes that the effectof a patient history-altering event can be quantified by a
multiplier to the baseline hazard. Instead, it may be reasonable to assume that the shape of the
baseline hazard is alteredby the occurrence of a nondeath event. Toaccomplish this, you could
stratify the analysis based on Event index.