Could someone please help me understand with an example what is the exact difference between left censoring and left truncation?? Thank you.
left censoring occurs when the exact time of event is not known because the experiment ended before that or the subject made a decrement in ways other than the mode of interest (event happening).All we know is the time when we stopped tracking it. Left truncation occurs when we entirely omit the record from the sample being studied, say by design constrants. Hence, for example, in a mortality study, if we chose only those above the age of 60, for their survival post heart surgery, this sample is left truncated to all those below age 60: we will never estimate their average life span post the procedure. Hope this helps
