Populations and samples
Populations and samples.
- The population is the whole group you want to describe; the sample is the part you observe.
- A census collects data from every member of the stated population.
Example 1
A school wants to know the views of all 800 students and surveys 60 of them. Identify the population and sample.
The population is the whole group the conclusion concerns. The sample is the part actually studied.
Example 2
A factory checks 40 light bulbs from a day’s production of 2400. Identify the population and sample for that day.
The population can consist of objects, not just people.
Your turn
A council asks 120 town residents about a new park. It wants the views of every resident. Identify the population and sample.
Check answer
Define the whole target group before describing the selected part.
A gardener studies 25 leaves taken from one tree to estimate the health of all leaves on that tree. Identify both groups.
Check answer
The population is this tree’s leaves, not every leaf in the garden.
A teacher records the test mark of every student in her class. Is this a sample survey of that class?
Check answer
Every member of the stated population is included.
A bus company surveys 90 passengers on Monday to study all passengers travelling that week. Identify the population and sample.
Check answer
Monday passengers may not represent the rest of the week; defining a sample does not make it representative.
A library selects 50 of its 3000 books to estimate the proportion needing repair. Identify the population and sample.
Check answer
The target population consists of books, not library members.
A council asks 120 town residents about a new park. It wants the views of every resident. Identify the population and sample.
AnswerDefine the whole target group before describing the selected part.
A gardener studies 25 leaves taken from one tree to estimate the health of all leaves on that tree. Identify both groups.
AnswerThe population is this tree’s leaves, not every leaf in the garden.
A teacher records the test mark of every student in her class. Is this a sample survey of that class?
AnswerEvery member of the stated population is included.
A bus company surveys 90 passengers on Monday to study all passengers travelling that week. Identify the population and sample.
AnswerMonday passengers may not represent the rest of the week; defining a sample does not make it representative.
A library selects 50 of its 3000 books to estimate the proportion needing repair. Identify the population and sample.
AnswerThe target population consists of books, not library members.