Populations, Samples and Censuses
Revise Populations, Samples and Censuses for GCSE Statistics with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA and Edexcel. A census collects data from every member of a population, while a sample collects from a representative part of it.
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These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA and Edexcel specifications. Every worksheet comes with a full mark scheme.
Topic overview
The population is the whole group being studied. A sample is a smaller part of the population selected to represent it. A census collects data from every member of the population.
A census gives completely accurate information about the population and includes every member, so there is no sampling error. But it is expensive, time-consuming, and often impractical for large populations. It may also be impossible if testing destroys the item.
A sample is quicker, cheaper and more practical, and it makes investigation of large populations possible. But it may not perfectly represent the population, and conclusions drawn from it are estimates rather than exact values.
Revision notes
The three terms
Population: the whole group being studied. Sample: a smaller part selected to represent it.
Census: data collected from every member of the population. Note that the population need not be people — it could be all the light bulbs made by a factory.
Census advantages and disadvantages
Advantages: completely accurate, every member included, no sampling error.
Disadvantages: expensive, time-consuming, often impractical for large populations, and impossible where testing destroys the item.
Sample advantages and disadvantages
Advantages: quicker, cheaper, more practical, and makes large populations investigable.
Disadvantages: may not perfectly represent the population, so conclusions are estimates. A larger sample is generally more representative but takes more time and money.
Key points
- The population is the whole group studied.
- A sample is a part of the population.
- A census collects data from every member.
- A census gives completely accurate information.
- A census is expensive and time-consuming.
- A sample is quicker but may not be representative.
Worked examples
Example 1
State what is meant by a census. [1 mark]
Working
Example 2
Give one reason why a factory testing light bulbs would use a sample rather than a census. [2 marks]
Working
Example 3
Give one advantage and one disadvantage of taking a sample rather than a census. [2 marks]
Working
Common mistakes
Thinking a population must be people.
It is any complete group being studied, including objects.
Saying a census is always better.
It is impractical for large populations and impossible for destructive testing.
Confusing sample and sampling frame.
The frame is the list; the sample is who is actually selected.
Giving only one side when evaluating.
Questions usually want both an advantage and a disadvantage.
Exam tips
- Define the population precisely before discussing sampling.
- Use destructive testing as your example of when a census is impossible.
- Give both sides when comparing census and sample.
- Remember a population can be objects, not just people.
Key terms
- Population
- The whole group being studied.
- Sample
- A part of the population selected to represent it.
- Census
- Data collected from every member of the population.
- Sampling error
- The difference between a sample result and the true population value.
Related topics
Written and reviewed against the current AQA and Edexcel specifications. Spotted an error? Let us know.