Repeated-measures experiments measure the same set of research participants two or more times, while matched-subjects experiments study participants who are matched on one or more characteristics. Which of the following are true for both a repeated-measures experiment and a matched-subjects experiment when used to compare two treatment conditions?

a. The researcher computes difference scores to compute a t statistic.
b. If the researcher has n number of participants to use in the experiment, then the degrees of freedom will be the same in a repeated-measures experiment or in a matched-subjects experiment.
c. The researcher must compute an estimated standard error for the mean difference score to compute a t statistic.
d. Participants in both types of experiments are all measured the same number of times.