Differential analysis & tests / Survival analysis (Kaplan–Meier)
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The step curves are Kaplan–Meier survival estimates with shaded confidence bands; tick marks show censored subjects (follow-up ended without the event). The table below gives the number still at risk at each time.
Median survival is the first time the curve reaches 0.5 or below; if it never does, it is shown as “not reached”. Its confidence interval uses the times at which the confidence band first reaches 0.5 (the usual convention).
The log-rank test compares whole survival curves; with more than two groups pairwise tests are added, adjusted by the method you choose. The test loses power when curves cross.
The event column may use 1/0, true/false or words such as dead/alive; for other codes state the value meaning “event occurred”. Times keep your input units.
Kaplan & Meier (1958) J Am Stat Assoc 53:457; Greenwood (1926); Mantel (1966) Cancer Chemother Rep 50:163 (log-rank). Survival estimates, CIs, medians and their CIs match lifelines KaplanMeierFitter; log-rank results match lifelines logrank_test / multivariate_logrank_test.
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