Capture-recapture is a sampling method which allows us to estimate the size of a population without counting it fully. It is very useful when the entire population may be too difficult to count.

Capture/recapture sampling method

Maths

Checking understanding of statistical problems

The Statistical Enquiry Cycle

Types of data

Sampling methods

Stratified sampling

Sampling limitations

Data collection

Biased questioning

Advanced problem solving with sampling

In this unit, pupils are given the opportunity to assess how valid a sample may be and what the averages might tell us. In the future unit, pupils extend their knowledge of averages to stem and leaf diagrams as well as comparing two data sets.

In the prior unit, pupils considered the mean, median and mode and evaluated their usefulness in a variety of contexts. In this unit, pupils are given the opportunity to consider where the data came from and how it was collected and can therefore start to evaluate how good a representation the sample is of the whole population.

In this unit pupils will learn how to sample, and explore accuracy and limitations with various sampling strategies and data collection techniques.

Sampling

__________ is a sampling method which allows you to estimate the size of a population without counting it fully.

Some hedgehogs may have chewed through the paper band.

Some hedgehogs may have lost the paper band when moving through hedges.

Izzy might have recaptured the same hedgehog twice.

Izzy needed to wait longer before recapturing the hedgehogs.

Izzy’s sample size might have been too small.

Izzy captures 10 hedgehogs and marks each one with a paper band around its leg. Izzy then recaptures 10 hedgehogs, but finds that none of them have a paper band. Select the possible reasons for this.

Some of the birds may have died or migrated

Not enough time was left between the capture and the recapture.

To estimate the population of birds in a wood, 5 birds are captured from a single tree and marked. 9 months later, in a recapture of 10 birds, 0 were marked. Which factors may effect the results?

As part of a capture-recapture sample, 100 fish from a lake are captured and marked with a white dye. During a recapture of 50 fish, 5 were marked with the white dye. Select the correct statement.

Andeep captures 15 deer and marks them by attaching a tag to their legs. Three days later, Andeep recaptures 30 deer, and 3 of them have a tag attached. Estimate the total number of deer. 

Jun captures 45 squirrels and marks them by attaching a tag to their legs. Three days later, Jun recaptures 70 squirrels, and 15 of them have a tag attached. Estimate the total number of squirrels. 

A PE teacher wants to split the students at her school based on the strata of the sport the student enjoys the most. Select the appropriate strata.

A {{}} may be split into groups or strata. A stratified sample is where a representative sample is taken from each stratum.  

Select the sample that is most representative of the population from the given strata: A hospital with 1800 patients and 200 staff.
A sample of 200 people is taken.

A company employs 250 band A workers, 350 band B workers and 200 Band C workers. A manager wants to take a stratified sample of 160 workers. How many workers from each band should be sampled? 

A bus company wants to take a sample of  1000 customers, stratified by age. The table shows the number of customers in each age group. The bus company should choose {{}} under-16s for the sample.

A bus company wants to take a sample of 500 customers, stratified by age. The table shows the number of customers in each age group. The bus company should choose {{}} 16-65 year olds for the sample.

Starter Quiz

A PE teacher wants to split the students at her school based on the strata of the sport the student enjoys the most. Select the appropriate strata.