Evangelical Christians have been smitten by the numbers bug. Missionaries, evangelists, pastors, and laypeople now absorb statistics like their daily dose of vitamins. Yet, a blind acceptance of stats, can be fatal to one's faith.

Years ago, a Christian friend lost her faith after reading the classic study Hellfire and Delinquency. The data showed: "Religion does not cause people to refrain from delinquent behavior." As a result, many scholars, including my friend, concluded that Christianity makes no difference in people's lives.

Ironically, one of the study's authors today uses Hellfire and Delinquency to illustrate faulty research because other scholars found that church attendance significantly reduced delinquency rates. Author Rodney Stark says, "What counts is not whether [an individual] is religious, but also the proportion of religious people in their environment."

Among Christians, sociological findings may be wrong because they confuse numbers with statistics. In 1984, one South African study claimed that members of independent charismatic churches supported apartheid. Yet, the study was invalid because it was based on a nonrandom sample of 30 people belonging to one congregation, from which the authors made completely invalid generalizations.

A similar misuse of statistics and sociological research may be found in some church-growth research. In a research thesis I have seen, conclusions were drawn about missionary strategy in a Latin American city on the basis of a sample of successful church leaders.

What the author did not recognize was that his sampling technique did not support the type of generalizations he was making. Instead of setting out to test a hypothesis scientifically, the author sought to prove his ...