Finding 770 teenagers willing to fill out a detailed questionnaire and likely to reflect the behaviour and attitudes of tens of thousands of their peers is a tricky matter.

The Irish Times could have visited three or four big, familiar schools in south Dublin, for example, and asked teachers to get all students to do the survey. Would they have been representative of Irish teenagers as a whole? Hardly. And students preparing to do the Junior Cert or, worse yet, the Leaving Cert, might not like to spare the time.

So it was decided Transition Year should be targeted. Through the Transition Year Curriculum Support Service, Aine Maguire got a list of more than 500 schools around the State offering the year and broke them down into region and the sex of students..

The idea was to pick 60 schools that, in terms of their location and gender makeup, would look just like the list of all 500 schools. For example, Munster had about 30 per cent of all the schools offering Transition Year, and 29 per cent of those Munster schools were girls-only. Applying those percentages, Maguire figured out that five of her 60 schools would have to be girls' schools in Munster. The particular five were selected entirely at random.

Letters were sent to the TY co-ordinators in the 60 schools. The letters explained the reasons for the research and offered entry to a draw for modest prizes as an incentive to participate. The letters also promised that the responses would be anonymous and kept in strict confidence. "No one except me and one or two close colleagues knows which schools were surveyed," Aine Maguire says.

The Irish Times also promised that the survey results and information would not be passed on to anyone else. So while you can read a selective summary of Maguire's research findings today in Media Scope, Coca-Cola, for example, can't buy the details of teenagers' answers.

The promises and incentives, plus a handy fax reply sheet, meant that after follow-up letters and phone calls and an extension on the deadline, no fewer than 32 of the 60 schools got one of their classes to respond - a very high percentage for responses to a postal questionnaire by market-research standards.