The alternative hypothesis, H1, is a statement of what the test is set up to establish. For example if comparing average annual rainfall in El Nino and ordinary years then we could have:

H0,that the two means are not equal, i.e. there is a difference between the two types of year..

The conclusion from the hypothesis test is either “Reject H0 in favour of H1.” or “Do not reject H0.” If H0 is rejected then the analysis usually continues by establishing, in this case, the extent of the difference between the two types of year.