GCSE · Sampling
Populations & samplesExam-style questions
What a population and a sample are and why we sample at all; why a representative sample matters more than a big one; and the two calculations that earn the marks — scaling a sample up to estimate a population total (including capture–recapture and its assumptions) and sharing a stratified sample out in proportion.
11 questions · GCSE (Higher) level · mark scheme and worked solution on each · no sign-up to try
- 1A conservation group wants to estimate the number of newts in a pond.
They catch newts, mark each one and return them to the pond.
A week later they catch newts. of these newts are marked.
Work out an estimate for the number of newts in the pond.Level 3 · 3 marksTry it - 2A company employs people at three sites.
A stratified sample of employees is to be taken.Site Number of employees Leeds Bristol Cardiff
(a) Work out the number of employees from Leeds that should be in the sample.
(b) The sample is to contain employees from Bristol.
Work out the number of employees from Cardiff that should be in the sample.Level 3 · 4 marksTry it - 3A town council wants to estimate how many of the town's residents use the town library.
They take a random sample of residents. of these residents use the library.
(a) Use the sample to estimate the number of residents in the town who use the library.
(b) The council repeats the survey using a new random sample of residents.
Explain why the estimate from this larger sample is likely to be more reliable.Level 3 · 3 marksTry it - 4A scientist wants to estimate the number of fish in a lake.
She catches fish, tags them and returns them to the lake. Later she catches fish and finds that of them are tagged.
(a) Estimate the number of fish in the lake. [2]
(b) State one assumption she has made. [1]
(c) Give one reason why asking her friends which fish they had seen would NOT be a good way to sample. [1]Level 3 · 4 marksTry it