What is the primary purpose of Kaplan-Meier curves in survival analysis?

What is the primary purpose of Kaplan-Meier curves in survival analysis?

• A. Kaplan-Meier estimates the survival function over time.
• B. Kaplan-Meier curves show hazard ratios.
• C. Kaplan-Meier curves compare means at a fixed time point.
• D. Kaplan-Meier is used to estimate incidence rates.

Answer: (A)

The main idea is estimating the survival function over time from time-to-event data that may be censored. Kaplan-Meier curves produce a step function of S(t), the probability of surviving beyond time t, by accounting for when events occur and by adjusting for individuals who are censored (lost to follow-up or study end). Each downward step reflects an event, and the curve remains flat between events because no new information changes the estimated survival probability. This makes it the standard way to visualize how survival changes over time and to compare groups, often with a formal test like the log-rank test. Hazard ratios come from models that describe the instantaneous risk of the event and are not directly read off a Kaplan-Meier curve. Comparing means at a fixed time ignores censoring and isn’t how survival data are typically analyzed. Incidence rates measure events per person-time, not the probability of surviving past each time point.

The main idea is estimating the survival function over time from time-to-event data that may be censored. Kaplan-Meier curves produce a step function of S(t), the probability of surviving beyond time t, by accounting for when events occur and by adjusting for individuals who are censored (lost to follow-up or study end). Each downward step reflects an event, and the curve remains flat between events because no new information changes the estimated survival probability. This makes it the standard way to visualize how survival changes over time and to compare groups, often with a formal test like the log-rank test.

Hazard ratios come from models that describe the instantaneous risk of the event and are not directly read off a Kaplan-Meier curve. Comparing means at a fixed time ignores censoring and isn’t how survival data are typically analyzed. Incidence rates measure events per person-time, not the probability of surviving past each time point.