Survival analysis

Kaplan-Meier curves, the log-rank test and the hazard ratio.

7 pages

Concept

• Actuarial life tablesThey estimate survival over fixed intervals (for example by year) when the exact date of each…
• Kaplan-Meier curveA step curve showing what share of people remain free of the event as time passes
• Survival analysis and censoringIt studies how long it takes until an event, making use of people whose follow-up ends before it…

Measure

• Five-year and relative survivalRelative survival compares patients with people of the same age and sex without the disease: it…
• Hazard ratio and the Cox modelThe HR compares how fast events happen in two groups

Statistical test

• Log-rank testIt compares whole survival curves: at each event it checks whether a group had more events than…

Bias

• Stage migration (Will Rogers phenomenon)Better staging moves patients to a more advanced stage: both stages seem to improve although…

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← Epidemiology, biostatistics and public health

Educational content on epidemiological and statistical methods; the examples use made-up numbers to teach the calculation. Not a clinical or legal guide: current Colombian rules are in the official sources.

Representative model, for educational purposes only.