Zowie
A marketing researcher wants to study how humor in television commercials affects sales.  To do so, the researcher studies the effectiveness of two commercials that have been developed for a new soft drink called Zowie.  One commercial, in which a well-known but serious television actor describes how Zowie has a zingy and refreshing taste, airs during the months of March, April, and May. 

The other commercial, a humorous scenario in which several teenagers spray one another with Zowie on a hot summer day, airs during the months of June, July, and August.  The researcher finds that in June through August, Zowie sales are almost double what they were in the preceding three months.  "Humor boosts sales," the researcher concludes.

Music
An industrial psychologist wants to study the effects of soft classical music on the productivity of a group of typists in a typing pool.  At the beginning of the month, the psychologist meets with the typists to explain the study, gets their consent to play the music during the working day, and then begins to have music piped into the office where the typists work. 

At the end of the month, the typists' supervisor reports a 30% increase in the number of documents completed by the typing pool that month.  "Soft music increases productivity," the psychologist concludes.

Teachers
An educational researcher wants to study the effectiveness of a new method of teaching reading to first graders.  The researcher asks all 30 of the first-grade teachers in a particular school district if they would like to receive training in the new method and then use it during the coming school year. 

Fourteen teachers volunteer to learn and use the new method; 16 teachers say that they would prefer to use their current approach.  At the end of the school year, students who have been instructed with the new method have significantly higher average scores on a reading achievement test than students who have received more traditional reading instruction.  "The new method is definitely better than the old one," the researcher concludes.