=+Does a “stop smoking” program work better if it costs more? Smokers responding to an advertisement offering to help them stop smoking were randomly offered a program Exercises M20_SHAR8696_03_SE_C20.indd 759 14/07/14 7:36 AM 760 CHAPTER 20 Design and Analysis of Experiments and Observational Studies costing $100 or the same program costing $250. The offer was made individually to each client by presenting a sealed