The case in three lines. The Green Gazette's front page says energy drinks double heart risk, quoting a university press release, and the canteen stops selling them. A reader writes in with two words: twice what? The study itself shows the risk going from about one in ten thousand a year to about two in ten thousand, and Tara has to write the corrections box.

One question to ask. "What should the box say?" Then: "If the headline was true, was it still misleading?" Let them argue both sides.

One thing to do at the table. Find a headline one of you has seen with "doubles", "triples" or "cuts by half" in it. Try to find the starting number. Put it next to something the size of your street or your school, and say both numbers out loud.

The grown-up layer. The case separates a relative risk (twice as likely) from an absolute risk (one more case in ten thousand), and a clarification from a retraction. It gives the school nurse her strongest point, that a small number can be heard as "safe". The habits it models are going past the press release to the study, asking "compared with what?", and keeping a warning while giving it its number.

The case leaves the line blank on purpose. Ask for it before you offer yours.