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Random and Stratified Sampling




 

This lesson can be used for revision for the higher Maths GCSE. The examples are quick and concise with exam style questions, go to GCSE Maths if you need more in-depth explanations.

What is a random sample?
In a random sample, every person in the population has the same chance of being selected.

What is a stratified sample? In a stratified sample, the proportion of each group is the same as the proportion in the whole population.

Example 1: A school has 650 students.
Each student studies one of Greek or Spanish or German or French. The table shows the number of students who study each of these languages.
An inspector wants to look at the work of a stratified sample of 70 of these students. Find the number of students studying each of these languages that should be in the sample.
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