What is meant by "the difference of the means" when talking about an independent samples t test? How does it differ from the "mean of the differences" in a related samples t test?
a. The difference of the means is the subtraction of one group's mean from the other in independent samples; it differs from mean of the differences in related samples, where each pair's difference is calculated first.
b. The difference of the means is the mean of all differences between paired observations, while mean of the differences is the mean of one group subtracted from the other.
c. The difference of the means is the mean of one group subtracted from the other in related samples; it differs from mean of the differences in independent samples, where each pair's difference is calculated first.
d. The difference of the means is the mean of all differences between paired observations, while mean of the differences is the subtraction of one group's mean from the other.