It is always appropriate to use a directional alternative hypothesis.

Question

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It is not always appropriate to use a directional alternative hypothesis. A directional alternative hypothesis should only be used when there is a clear theoretical or logical reason to expect that the mean or proportion being tested will be higher or lower than the null value. In some cases, a non-directional alternative hypothesis may be more appropriate, such as when the researcher is unsure about the direction of the effect.

It Is Always Appropriate to Use a Directional Alternative Hypothesis