A situation in which I would test a directional hypothesis would be a drug companys new antidepressant. ?The directional

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A situation in which I would test a directional hypothesis would be a drug company’s new antidepressant.  The directional hypothesis I would test is that the drug helps those dealing with symptoms of depression in a positive way, either by reducing or eliminating depressive moods, thoughts, and/or behaviors.  The independent variables would be whether or not a participant in the study received the drug or the placebo. The dependent variables would be whether or not the drug affects the participants moods, thoughts, and/or behaviors.  This hypothesis is directional because it states that the drug positively affects the participants moods, thoughts, and/or behaviors; therefore, I am operating under the assumption that the drug either does these things or simply does not do them.

Using the same situation, I could create a nondirectional hypothesis: the new antidepressant will have an effect on the participants moods, thoughts, and/or behaviors. The independent and dependent variables remain the same; however, my hypothesis is now a nondirectional one.  It is nondirectional because it states the drug will have some effect, but does not say what that effect will be, thus I am not stating which direction I expect the results to go. 

The more appropriate test, in my opinion, is a one-tailed directional test.  This is because I specifically want to know whether or not this drug is going to positively effect the participants.

It is important, in regards to a two-tailed test, to alter the alpha level to create a rejection region of 5%, instead of having a total of 10%.  As stated in our lectures, in a two-tailed test, we would “reject the mean for a total of 10% of the scores and not just 5%.”  In addition, the tails on a two-tailed test are commonly smaller than a one-tailed test, thus in order to reject the null, the “test statistic needs to be a more extreme score.”