A two-sample test with n1=5 and n2=6 would have how many degrees of freedom for the critical value assuming normality

a. 9

b. 10

c. 11

d. None of the above

A independent two-sample test with n1=34 and n2=42 would have how many degrees of freedom for the critical value?

a. 34

b. 72

c. 74

d. None of the above

A statistical test involves a "before and after" focus with 12 subjects has how many degrees of freedom?

a. 11

b. 12

c. 24

d. None of the above

df = n1+ n2 - 2

Is this used for every one or is there a different formula to use? The only other formula I have is for t-test for unequal variances.

Also how do you now if you have unequal variances or equal variances when looking at problems?