2.1.17—Capture-mark-release-recapture
- Syllabus
- First assessment 2026
- Objective
- 2.1.17
- Level
- HL
Use the Lincoln Index with Its Assumptions
Lincoln estimate N = M × C ÷ R, where M is marked first capture, C total second capture and R marked recaptures.
Assume a closed population, no mark loss or effect, mixing and equal capture chance. Low R makes the estimate unstable.
Mark 40, catch 50 later and recapture 10 marked: N = 40×50÷10 = 200.
The estimate rises to 400; a low recapture count makes it sensitive to small sampling changes.
C is the total second sample; R is only marked recaptures.