Paired t-Test
The paired t-test analyzes paired data by converting each pair into a difference and then performing a one-sample t-test on those differences.
If $d_i = y_{Ai} - y_{Bi}$, the test is based on
$$t = \frac{\bar{d} - d_0}{s_d / \sqrt{n}}.$$R
t.test(yA, yB, paired = TRUE)
Equivalent one-sample formulation:
d <- yA - yB
t.test(d)