Collecting data and sampling · Grade 7
In Grade 7 you learn: populations and samples.
To learn about a whole population, you usually collect data from only a sample. A good sample is big enough and represents the population fairly. A biased sample gives misleading results, however carefully you analyse it.
Key facts
- Population: everyone or everything you want to find out about. Sample: the part you actually collect data from.
- Capture–recapture: N ≈ number marked × size of second catch ÷ number marked in the second catch.
Worked examples
Example 1
40 fish are caught, tagged and released. Later 50 fish are caught and 8 of them have tags. Estimate the number of fish in the lake.
Answer: About 250 fish