SAMPLINGWhen you want to select a sample from a large number.

For example, select 50 people from a list of 400 people.

There are many methods to take a sample.

For GCSE maths, you need to know about:

–Simple random sampling.

–Stratified random sampling.

SIMPLE RANDOM SAMPLING

Everything has an equal chance of being included in the sample.• Give everything a number.• Use a random number table or a calculator to select the sample.

Example: From 758 students (numbered 1 to 758), select 15 students.

191, 842, 347, 182, 103, 597, ……

OR use RAN# on your scientific calculator.

STRATIFIED RANDOM SAMPLING

Everything is put into categories first. (gender, age groups, year group,…)

A sample is chosen from each category in the same proportion to the whole population.

Example: A sample of 50 students is to be taken.How many pupils would you select from each year group?

Year 7 162

Year 8 161

Year 9 157

Year 10 63

Year 11 58

TOTAL = 601