A researcher wanted to test the effect of a new drug on reducing blood pressure. In the study, there were 35 participants. The researcher measured the participants’ blood pressure before and after the drug was administered. If we want to compare the mean blood pressure from the two time-periods with a two-tailed t test, how many degrees of freedom are there?
a.34
b.35
c.68
d.69
e.70
Not sure if i did this right but I was thinking the answer was A since DF= 35-1 = 34. Is that right?
I believe it is n-2 when doing a two sample t.
Yes, you are correct. In order to calculate degrees of freedom (DF) for a two-sample t-test, you need to subtract 1 from the total number of participants in each group. In this case, there were 35 participants, so the degrees of freedom would be 34 (option a).
The reasoning behind subtracting 1 is that when comparing the means of two groups, one degree of freedom is used to estimate the overall population mean, leaving the remaining degrees of freedom to account for the variation within each group.