A study by the Readership Institute10 at Northwestern University used survey data to analyze how reader behavior was influenced by the Iraq war. The response variable was a Reader Behavior Score (RBS), a combined measure summarizing newspaper use frequency, time spent with the newspaper, and how much was read.

ComparingRBSscores before the war and during the war, the study noted that there was a significant increase in reading by light readers (mean RBS changing from 2.05 to 2.32, P < 0.001) but a significant decrease in reading by heavy readers (mean RBS changing from 5.87 to 5.66, P < 0.001).Would you conclude that the Iraq war caused a change in reader behavior, or could there be some other explanation?