The pool from which Impact newspapers
were drawn comprises English-language U.S. dailies, publishing at least
five days a week, with average circulation of more than 10,000. Specialist
newspapers and newspapers with significant national distribution were
To select a group of newspapers from
that pool that would be as representative of the industry as possible,
researchers at the Readership Institute used a stratified sampling method
that took into account seven variables, including competition, circulation,
penetration, urbanicity, and market size and potential.
Analysis of the newspaper industry using
these variables yielded six strata. The strata reflect size, market
and competitive situation. Between 16 and 18 newspapers were then randomly
selected from each stratum.
While circulation was only one of the
variables used in determining the six strata, people frequently ask
about the distribution of circulation sizes in the sample. The chart
above shows what the circulation groups look like.