In life data analysis, what does 'right-censored' data mean?

• A. All lifetimes are fully observed.
• B. Life times of some units are not observed within the study period; the data are right-censored.
• C. Censored data means data that are lost.
• D. Censored data are those with incorrect timestamps.

Answer: (B)

Right-censored data in life data analysis means we don’t know the exact lifetime for some units because the study ends before the event occurs (or the subject is lost to follow-up). For those units, we only know that their lifetime is at least as long as the observed time up to the censoring point. For example, if a subject is followed for five years and is still alive, their true lifetime is at least five years but could be longer; that five-year observation is right-censored. This lets us use the available information without claiming an exact endpoint we can’t observe. The other options aren’t correct because fully observed lifetimes aren’t censored, censoring isn’t simply data being lost, and censoring isn’t about incorrect timestamps—it's about incomplete observation.