When the survey instrument is quite long, a(n) ____ is preferable.
a. personal interview
b. e-mail questionnaire
c. group questionnaire
d. phone interview
Question 2
Which of the following must be controlled in research on perception?
a. the motivation of the observer
b. the emotional content of the material presented to the observer
c. the physical characteristics of the stimulus that are not being investigated
d. all of these