For the ninth edition of CALCULUS, the authors analyzed the copious data they receive from their website, http://www.CalcChat.com
The site offers free solutions to odd-numbered exercises in the text. The site currently has over 1 million hits per month. The authors analyzed these hits to see which exercise solutions students were accessing most often. They revised and refined the exercise sets based on this analysis. The result is the only calculus book on the market that uses real data about its exercises to address student needs.