What is the number of degrees of freedom associated with the t-test, when data are gathered from a matched-pairs test with 20 pairs?

Question

What is the number of degrees of freedom associated with the t-test, when data are gathered from a matched-pairs test with 20 pairs?
a.
18
b.
19
c.
20
d.
38

Answer 1

Even though you have 2 samples they are paired so the degrees of freedom will be: 

df = n-1

When you have marched paired sample its as if working with one sample.