a research hypothesis; the hypothesis that is supported if the null hypothesis is rejected.
In general, the proposition expressing the particular way the null hypothesis is held to be false. Sometimes referred to as the motivated hypothesis, it usually reflects a difference the researcher hopes to demonstrate. In the ANOVA setting, the usual alternative hypothesis is that the true means of the various groups are unequal.
Sometimes we propose an alternative to the null hypothesis, to be accepted if the null hypothesis is rejected. If the null hypothesis is that the mean is three, we reject it if the mean is not three. The alternative hypothesis may state that the mean is 3.5. Note that it is possible to reject both the null and alternative hypotheses. (The statement that the mean is not equal to three is known as the complement of the null hypothesis.)