# Terminology: one-sided/two-sided hypothesis test

What is meant by a one-sided/two-sided hypothesis test? Is it just another term for a one-tailed/two-tailed hypothesis test?

And is a hypothesis test necessarily either one-tailed or two-tailed, or it could be neither?

• What do you have in mind when you say non-tailed test? – RScrlli Mar 28 '19 at 8:39
• I confess that I am not really sure. – Noppawee Apichonpongpan Mar 28 '19 at 8:57
• Answer to your first question is 'yes', though the second terminology is somewhat more used I guess. – StubbornAtom Mar 28 '19 at 10:03
• For instance in OLS framework sometimes you are interested is testing whether $b=0$ or not, in this case you use a two tailed test cause it could happen that $b<0$ or $b>0$. Instead if you wanna test for instance $b<0$ you will use a one tailed test. – RScrlli Mar 28 '19 at 10:46