The TRIPSE - example problem Next Page | TOC | Home

Leading Causes

Marnie, a graduate student in Behavioural Sciences, uses a well validated rating scale to assess the prevalence of antisocial behaviour amongst Grade 3 students in all 5 elementary schools in the city. She finds that 27 out of 246 can be labelled "antisocial". Closer attention to the data shows that 7 out of the 27 students come from the same private school (The Vanguard).

Millicent, who is Marnie's roommate, suggests that she approach the problem epidemiologically by listing the school as a "risk factor" for the production of antisocial behaviour. She shows Marnie how to tabulate the data to estimate an odds-ratio. 

  Antisocial behaviour Normal behaviour
The Vanguard 7 18
All other schools 20 201

The estimated odds-ratio is large enough to cause concern. At Millicent's urging, Marnie decides to explore the issues further.

She finds that the school is a private one, run by a Society dedicated to improving the lot of women. Many of the mothers who send their children to the school are adamant about self-reliance. To that end they not only promote self-medications with herbals rather than prescription drugs, but also advocate that women undertake training in using firearms. A large number of them are practising artists and craftspeople. Marnie is also intrigued to find that 5 of the 7 students on her list live in the same large house — an older building which had been extensively remodelled several years ago by the parents themselves. The house not only has several pottery studios but also an attached indoor shooting range.

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