About Truncation Types
Truncation (Pemancungan): A selection mechanism by design. Only subjects satisfying certain conditions regarding their survival time are included.
Left Truncation (Delayed Entry)
Subject enters study after time 0; only observed if .
Examples:
- Nursing home: Subjects must survive long enough to enter
- Life insurance: Policyholders must be alive when signing up
Right Truncation
Subject exits study before event; only observed if .
Example: Historical death records—only people who have already died are included.
Comparison with Censoring
| Feature | Censoring | Truncation |
|---|---|---|
| Nature | Missing information about exact time | Selection bias by study design |
| Awareness | Researcher knows subject exists | Researcher may not know excluded subjects exist |