In an experiment, a researcher manipulates people's mood to determine whether changes in mood cause changes in memory performance. However, the researcher is not sure that the manipulation is really causing people's mood to change. In this case, what should the researcher do?
a. Control mood by holding it constant.
b. Control mood by matching it across treatment conditions.
c. Add a no-treatment control group in which mood is not manipulated.
d. Add a manipulation check by measuring mood.
Question 2
Tonja wants to evaluate the effects of a new school breakfast program on student conduct and academic achievement. She cannot evaluate every student in every school in the district, so she randomly selects several schools and then collects data on all of the students in those schools. What type of sample is she using?
a. simple random
b. stratified random
c. systematic random
d. cluster random
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