You decide to implement the simple one-factor completely randomized design, sending out four offers (Coupon, Card, Movie, or No Offer) to 4000 students each (see For Example: “Designing an experiment for Ottawa–Toronto flights”). A year later you collect the results and find the following table of means and standard deviations:

An ANOVA table shows:

QUESTION: 

What conclusions can you draw from these data?

Level Number Mean Std Dev Std Err Mean Lower 95% Upper 95% Coupon 4000 15.17 72.30 1.14 12.93 17.41 Card 4000 11.53 62.62 0.99 9.59 13.47 Movie 4000 13.29 66.51 1.05 11.22 15.35 No Offer 4000 9.03 50.99 0.81 7.45 10.61