First, this study did not exactly involve a nationally representative sample of taxpayers.

This study examined 10 independent samples designed to be nationally representative, based on data from more than 8,500 participants.

Mintel spoke to more than 2,000 people in a nationally representative survey.

The test is always given first to a nationally representative sample of graduating high school seniors to determine where the passing level should be set.

The findings come from a nationally representative survey of 903 teens with drivers' licenses at 26 high schools.

She said the survey would be conducted from a nationally representative sample of all races.

The study, conducted since 1975, surveys a nationally representative sample of about 50,000 students in 400 public and private schools.

They said the quality of sampling procedures was well above the level common in national surveys, using a large, nationally representative survey.

A few students were tested even in the six states that did not participate fully, allowing the collection of a nationally representative sample.