Calculate degrees of freedom for each of the following designs:
a. Forty students were recruited for a study about the relation between knowledge regarding academic integrity and values held by students, with the idea that students with less knowledge would care less about the issue than students with greater amounts of knowledge.
b. Twenty-seven couples are surveyed regarding their years together and their relationship satisfaction.
c. Data are collected to examine the relation between size of dog and rate of bone and joint health issues. Veterinarians from around the country contributed data on 3113 dogs.
d. Hours spent studying per week was correlated with credit hour load for 72 students.