populations, samples and collecting data
Take random samples of 10 and of 50 from a school of 600 pupils and compare them with the whole school. Spot a biased sample, and choose the right way to collect data for each question.
- UK: Year 10
- Iran: grade 10
- Afghanistan: grade 7
- Palestine: grade 11
- Ukraine: grade 9
- Russia: grade 11
Guide
This studio follows GCSE S1 (populations, samples and bias), Iran's Year 10 lesson «جامعه و نمونه» and the Afghan Year 7 chapter on collecting information. The population is everyone we want to know about (here, the 600 pupils of a school). A sample is the part of the population we actually look at. The closed bag is the population: we don't know how many pupils walk to school, and each draw picks one pupil at random.
The big ideas: a sample's result is only an estimate; every random sample gives a slightly different result; a bigger sample is usually closer to the population, as long as it is random. A big but biased sample (only the sports team members, say) still gives the wrong answer.
Four ways to collect data: a questionnaire (asking people), observation (watching and recording), an experiment (changing one thing and measuring what happens) and records (registers and files that already exist). A common mistake is to think a convenient sample (your own friends) is random.