How to choose between a two tailed and one tailed T-test with scipy?

Question

Scipy website seems to be down again :(

I am conducting a paired t test. But I am not sure how to choose between two-tailed and one-tailed (I need to use two-tailed). And also the ttest_reul only return t and p values. Anyway to find out degrees of freedom? Many thanks

from scipy import stats
t_val_Input, p_val_Input = stats.ttest_rel(c1,c2)

Answer 1

From the docstring of ttest_rel :

ttest_rel(a, b, axis=0, nan_policy='propagate')

Calculates the T-test on TWO RELATED samples of scores, a and b.

This is a two-sided test for the null hypothesis that 2 related or repeated samples have identical average (expected) values.

"Two-sided" means two-tailed.

The degrees of freedom is n - 1 , where n is the number of pairs (ie len(a) or len(b) ).