We limited our sample to the set of newspapers with a daily circulation of more than 100,000, as listed in the 2005 edition of Bacon’s Newspaper Directory… The initial subject pool consisted of 116 newspapers nationwide, but was then narrowed down to our final sample size of 100 because of factors that mandated exclusion of certain papers including bankruptcy of the newspaper since 2005, papers printed primarily in a foreign language, or data coding problems such as returned to sender submissions of letters.
After each newspaper was randomly assigned into one of the two treatments, the appropriate letters were submitted via email and online submission forms on Monday, October 20, and Tuesday, October 21, 2008.
We randomized whether the letter to the editor they received was pro-Obama or pro-McCain.
Whether the newspaper was interested in publishing the letter.
Butler, Daniel M. & Emily Schofield