How to get full marks on a systematic sampling question (GCSE Statistics)

The method in three steps

• Work out the interval: population size divided by sample size. For 30 people from 300, that is 300 ÷ 30 = 10.
• Choose a random starting point between 1 and the interval, for example by using a random number generator.
• Select that item and then every interval-th item after it (for example the 4th, 14th, 24th and so on).

Where students lose marks

• Saying “every 10th person” without showing where 10 comes from.
• Starting at the first person instead of choosing a random start.
• Forgetting that the list needs to be ordered or numbered first.

Practise it with feedback

PrepAcer's written-answer questions are marked against a list of mark points, and every point is shown as met or missed so you can see exactly where a mark was gained or lost. If you think a mark is wrong there is a “Question this mark” button.

Try the sampling questions in the free GCSE Statistics sample.