9. A repeated-measures design also is referred to as a paired-samples design because a first set of scores is paired with a second set of scores. Which of the following is NOT an example of paired data and hence could not be analyzed using a repeated- measures t test?

a. Scores acquired from the same group of individuals measured under two separate conditions.

b. Scores acquired from two separate groups of unrelated individuals who have been matched on a specific attribute such as age or IQ.

c. Scores acquired from separate groups formed by assigning naturally occurring pairs of individuals-one person to each group-such as married couples, sib- lings, and identical twins.

d. Scores acquired from two separate groups of unrelated individuals who have been randomly assigned to each group.