In a statistical hypothesis test:

• The null hypothesis, [latex]H_{0}[/latex], is what we assume to be true to begin with. It is often a statement of no change from the previous value or from what is expected.
• The alternative hypothesis, [latex]H_{A}[/latex], is what we consider to be plausible if the null hypothesis is false. Often, it is a change from the null hypothesis that we would like to test the accuracy of. The alternative hypothesis answers the question, “Do we think the actual parameter is larger than, smaller than, or just different from the null value, where the null value is the value specified in the null hypothesis?”