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Difference between one-sided and two-sided p-values

Difference between one-sided and two-sided p-values


What is the difference between one-sided and two-sided values? And what are they exactly?

1 Answer

365 Team

Hello Tess,
We’re glad that you reached out.
If the alternative hypothesis is (say for test on one mean) Ha: µ < 50 or Ha: µ > 50 we have one sided test. For Ha: µ > 50 the direction is to the right (right-tailed test). For Ha: µ < 50 the direction is pointing to the left (left-tailed test). On the other hand, the alternative hypothesis Ha: µ ≠ 50 does not specify the direction, towards right or left hence we have two-sided test.
Additionally, for 5% alpha, here are the graphs related to rejection region of one sided and two sided tests.

You may also want to check on for more detailed explanation of the sides of the test.
Hope this helps.
The 365 Team

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