Which statement correctly describes censoring and right-censoring in cohort studies?

• A. Censoring is when adverse data are missing in a formal way.
• B. Censoring occurs when outcome data are incomplete; right-censoring occurs when a participant does not have the event by study end; affects risk estimation and requires survival analysis methods.
• C. Right-censoring means the event happened earlier than observed.
• D. Censoring only affects the sample size.

Answer: (B)

In cohort studies, censoring describes a situation where we don’t know the exact time to the event for some participants because observation ends or they drop out. Right-censoring specifically means that a participant has not experienced the event by the end of the study (or by their last follow-up); we know they were event-free up to that time, but we don’t know what happens after. This incomplete information matters for estimating risk and time-to-event outcomes, so survival analysis methods (like Kaplan-Meier curves or Cox models) are used to properly incorporate these censored observations into the analysis.

The other statements don’t fit because censoring isn’t simply “adverse data missing” in a formal sense, and censoring affects more than just sample size. Also, right-censoring does not mean the event happened earlier than observed; it means the event has not occurred by the end of observation.