Ecologists use the mark-release-recapture technique to estimate the population size of mobile animals in a habitat.
A sample of the population is captured, counted, marked harmlessly, and then released. After a period of time, a second sample is captured, and the number of marked individuals (recaptured) is recorded.
The population size can be estimated using the following equation:
estimated population size=number marked in first sample×size of second samplenumber of recaptured animals \text{estimated population size} = \frac{\text{number marked in first sample} \times \text{size of second sample}}{\text{number of recaptured animals}} estimated population size=number of recaptured animalsnumber marked in first sample×size of second sampleAn ecological survey was conducted to investigate how the population of woodlice in a woodland habitat changed between May and September.
| Month | Number marked in first sample | Size of second sample | Number of recaptured animals | Estimated population size |
|---|---|---|---|---|
| May | 50 | 60 | 20 | 150 |
| September | 40 | 45 | 15 | ? |
Using the data in Table 1, calculate the difference in the estimated population size of woodlice between May and September.
