Idea 7of 22Builds onThe population and the sample
Ask everyone, or ask some?
When do you ask everyone, and when only some?
Today you'll discover
- what a census is
- why a sample is often better
- when only a census will do
Think firstJonah could ask all 60
Why might a survey ask 10 students instead of all 60?
Decide first, then press Next. Compare the work of asking 60 with asking 10.
The same 60 students. First a dashed outline goes round all 60: everyone is asked, a census. The bars at the right show 18 of 60 want a court. Then a sample of 10 names from a hat: 3 of 10 want a court, the same 3 in 10. The last step asks about T-shirt sizes.
See the whole ideathe big idea and the key word, in one place
The big idea
A census asks everyone; a sample asks some, and is faster, cheaper and easier.
Compare themCensus: every person, the exact answer, slow and costly. Sample: some people, a close answer, quick and cheap.
Canada's censusCanada holds a census every five years. Most other surveys use samples, because asking millions of people takes a long time.
Key word
- census
- collecting data from every member of the population, with nobody left out
Ready to use it?
- Decide whether a census or a sample fits a question.