Design of the Month

Moore's team has used a cluster trial to test an anti-smoking project that cunningly exploits peer pressure, for instance. More than 10,000 pupils aged 12 to 13 in 59 English and Welsh schools took part.

In half the schools, researchers polled all the pupils to identify the most influential ones in their year. Typically, the top-scoring 30 pupils from each school were then invited to a two-day training course about the harmful effects of smoking and how they could encourage their friends not to take it up. Moore's team found that pupils in these schools were 25 per cent less likely, on average, to start smoking over the following two years than those in schools where pupils only had conventional anti-smoking lessons (The Lancet, vol 317, p 1595).