Statistics, Year 7: asking questions of data

Posing a question

HintYou cannot collect anything until you know what you want to find out.

The whyWhat you ask decides what data to collect, from whom, and how to present it. Without it, a chart is only decoration.

Interpreting the results

HintIt means deciding what the charts are telling you.

The whyInterpreting means saying what the results show and what they do not. It often raises a new question, which is why it is called a cycle.

'Do more Year 7s at our school play football than netball?'

HintChoose the one you could settle by counting.

The whyA statistical question names who is being asked about and what will be counted. 'Good' is an opinion that no tally can settle.

No — the sample is too small and from one place

HintAsk who was left out.

The whyTwenty pupils from one class tell you about that class. A different school, in the countryside for example, could give a very different result.

No — friends are not a fair sample of the school

HintPeople who sit together often like the same things.

The whyA sample should represent everyone the question is about. Your friends are probably your age and may share your tastes.

35 minutes

HintCount up to the hour, then on.

The whyFrom 09:45 to 10:00 is 15 minutes, and from 10:00 to 10:20 is another 20. That makes 35.

25 minutes

HintFind the first departure after you arrive.

The whyThe 14:35 has already gone, so the next bus is the 15:05. From 14:40 to 15:05 is 25 minutes.

£2.50

HintThe note under the table changes the unit.

The why250p ÷ 100 = £2.50. Units and footnotes are part of the table, and they are easy to miss.

6

HintPool everything, then deal it out.

The why3 + 5 + 6 + 10 = 24 sweets, and 24 ÷ 4 = 6 each. This equal share is exactly what the mean is.

40

HintReverse the sharing.

The whyIf five numbers level out at 8 each, they must add up to 5 × 8 = 40. Total = mean × count.