Buzz was curious about the effect of coffee on sleep. He designed a study in which participants were randomly assigned to drink either 4 ounces or 24 ounces of coffee per day. He thought the amount of sugar people put in their coffee might affect sleep as well, so he randomly assigned half of the participants in each of his coffee conditions to use 1 teaspoon of sugar and half to use 3 teaspoons of sugar. Buzz thought that college students might get less sleep than adults who were not attending college, so he only used college students as participants in his study. Buzz also thought that the number of classes a college student was taking might impact how much sleep they got, so he ensured that all of the participants in his study took the same number of classes. Participants drank their assigned amount of coffee and sugar for two weeks, and Buzz asked them to report how many hours they slept during the same two-week period. Buzz's study is an example of a pretest/pottest design quasi-experimental factorial design true experiment factorial design Ex-post facto design