I'm consulting with a local quantitative person about some data, it's double-censored. Left censored is below limit of quantitation. Right censored is saturation of the assay. I want to regress it against a simple numeric predictor. I was just told that using survival analysis may not be appropriate because "the censoring is not independent of the outcome". Aren't so-called Tobit models also censored "independent of the outcome", but they can be run via a wrapper function in AES that just calls survreg?

I'm simply confused.


1 Answer 1


There's no problem with this type of censoring.

A review by Leung et al. explains the potential problems with censoring. In your case, the upper limit (right censoring) is essentially what they call "Type I censoring," in a clinical context "a study in which every subject is under observation for a specified period $C_0$ or until failure." In your case, an actual measurement is equivalent to an observed time "until failure" and your saturation level is equivalent to $C_0$. A similar argument applies to the left censoring of values below the limit of quantitation. These are equivalent to what's considered administrative censoring based directly on study design.

Problems arise when there is censoring due to things like loss to follow up in clinical studies. For example, if someone is close to death, too sick to show up for a clinic visit, and further information isn't available, the fact that the individual was lost to follow up might be considered troublingly informative. But that's not the case in your situation.

  • $\begingroup$ I think what may have confused the local expert is that I mentioned using survival models on data not concerned with survival. $\endgroup$
    – Bryan
    Apr 4 at 19:08
  • $\begingroup$ @EdM your opinion and suggested required stats.stackexchange.com/questions/611867/… $\endgroup$
    – PesKchan
    Apr 4 at 19:35
  • $\begingroup$ @Bryan I have the advantage that I remember Tobin from my college days. That might make it easier for me to see the connection to the survival analysis that I perform. $\endgroup$
    – EdM
    Apr 4 at 21:19

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.