Lincoln Index Method Calculator

How to Use This Calculator

1. Enter the number of individuals marked in your first sample (M). These should be marked in a way that they can be easily identified in subsequent samples.
2. Enter the total number of individuals in your first sample (N₁).
3. Enter the number of marked individuals recaptured in your second sample (R).
4. Enter the total number of individuals in your second sample (N₂).
5. Click the "Calculate" button to compute the estimated total population size and its 90% confidence interval.

Principle of Lincoln-Petersen Index

The Lincoln-Petersen index is a statistical method used to estimate the size of a population by capturing, marking, and then recapturing a subset of individuals. The formula assumes that:

• The marking does not affect the behavior of the animals
• The population is closed (no immigration or emigration during the study)
• Each individual has an equal chance of being captured in both samples
• The marked individuals are mixed randomly with unmarked individuals between sampling events

Example Scenario

Imagine you want to estimate the population of deer in a forest:

1. You capture 50 deer, mark them, and release them back into the forest (M = 50)
2. The total number of deer captured in the first sample was 100 (N₁ = 100)
3. The next day, you capture 70 deer, and 10 of them are marked (R = 10)
4. The total number of deer in the second sample was 150 (N₂ = 150)
5. Using the calculator with these values, you would estimate the total deer population and its confidence interval

Limitations

The Lincoln-Petersen method works best with large, closed populations. For small populations or those with significant immigration/emigration, the estimates may be less accurate. Also, the method assumes equal capture probability, which may not be true in all field conditions.