Statistics, Year 7: asking questions of data

Posing a question

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

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

Interpreting the results

提示It means deciding what the charts are telling you.

为什么Interpreting 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?'

提示Choose the one you could settle by counting.

为什么A 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

提示Ask who was left out.

为什么Twenty 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

提示People who sit together often like the same things.

为什么A sample should represent everyone the question is about. Your friends are probably your age and may share your tastes.

35 minutes

提示Count up to the hour, then on.

为什么From 09:45 to 10:00 is 15 minutes, and from 10:00 to 10:20 is another 20. That makes 35.

25 minutes

提示Find the first departure after you arrive.

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

£2.50

提示The note under the table changes the unit.

为什么250p ÷ 100 = £2.50. Units and footnotes are part of the table, and they are easy to miss.

6

提示Pool everything, then deal it out.

为什么3 + 5 + 6 + 10 = 24 sweets, and 24 ÷ 4 = 6 each. This equal share is exactly what the mean is.

40

提示Reverse the sharing.

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