Optional extension: Stratification, capture–recapture and sample precision
Example 1
A population has two strata as shown. Assuming each sample is representative of its stratum, estimate the total number who support the proposal.
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Answer: 310
- Apply each sample proportion to its own stratum.
- 200×10030+500×10050=310.
Example 2
Estimate the population using capture–recapture: N≈marked in second catchinitially marked×second catch. Assume a closed population, thorough mixing and equal catchability. Give an exact fraction if needed.
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Answer: 1000
- N≈360×50=1000.
Example 3
A population has two strata as shown. Assuming each sample is representative of its stratum, estimate the total number who support the proposal.
Show worked answer
Answer: 210
- Apply each sample proportion to its own stratum.
- 200×10030+300×10050=210.