The hypothesis actually to be tested is usually given the symbol H0, and is commonly referred to as the null hypothesis. As is explained more below, the null hypothesis is assumed to be true unless there is strong evidence to the contrary – similar to how a person is assumed to be innocent until proven guilty.
The other hypothesis, which is assumed to be true when the null hypothesis is false, is referred to as the alternative hypothesis, and is often symbolized by HA or H1. Both the null and alternative hypothesis should be stated before any statistical test of significance is conducted. In other words, you technically are not supposed to do the data analysis first and then decide on the hypotheses afterwards.
In SAS,
NULL hypothesis normally assumes there is no significant difference between the two models to be compared.
Alternative hypothesis assumes there is a significant difference between the two models.