Type I and II Censoring

So-called Type I censoring describes the situation when a test is terminated at a particular point in time, so that the remaining items are only known not to have failed up to that time (e.g., we start with 100 light bulbs, and terminate the experiment after a certain amount of time). In this case, the censoring time is often fixed, and the number of items failing is a random variable. In Type II censoring the experiment would be continued until a fixed proportion of items have failed (e.g., we stop the experiment after exactly 50 light bulbs have failed). In this case, the number of items failing is fixed, and time is the random variable.
Data sets with censored observations can be analyzed via Survival Analysis or via Weibull and Reliability/Failure Time Analysis . See also, Single and Multiple Censoring and Left and Right Censoring .