Which of the following is a disadvantage of central-location telephone interviews?
a. They have increasing costs due to respondent refusals to participate.
b. They tend to be slow, requiring the longest timespans per interview.
c. The federal "Do Not Call" law prevents people from being contacted for survey research.
d. The federal "Do Not Call" law prevents people from being contacted for survey research.
Answer: a. They have increasing costs due to respondent refusals to participate.