State the degrees of freedom and the type of test (repeated measures or matched pairs) for the following examples of measures for a related-samples t test:
(a) The difference in coping ability in a sample of 20 brothers and sisters paired based on their relatedness
(b) The difference in comprehension before and after an experimental training seminar in a sample of 30 students
(c) The difference in relationship satisfaction in a sample of 25 pairs of married couples
(d) The difference in athletic performance at the beginning and end of an athletic season for 12 athletes