Today we do a whole survey. We ask a question, collect the answers, show them in a chart so we can see them at a glance, and say what the chart tells us.

A good survey question has a short list of answers to pick from, and every pupil fits exactly one of them.

Before any hands go up, check the list: is each answer clear, and does every pupil fit exactly one?

A data detective works through five steps in order:

• Pose a clear question.
• Collect fairly with a tally.
• Turn the tally into a frequency table. The frequency just means how many times that answer came up — the one number for each row.
• Display it as a bar chart.
• Write a conclusion.

Here is how a finished cycle works. If Walk has twelve tally marks, its frequency is 12. That 12 sets how high Walk's bar goes: twelve marks, twelve high. Every bar is set the same way, count the marks, and the frequency is the height.

Now we collect our own. Today we run the survey: What is your favourite break-time game? We agree on four answers first, then each of you calls yours out and a pupil at the board adds a tally mark to the right row.