The six steps and stating the hypotheses

In short

• A hypothesis is a claim about a population parameter (a mean, a variance). We judge it with a sample statistic.
• The null hypothesis $H_0$ is presumed true until the data argue strongly against it. It always holds the equality: =, ≤ or ≥.
• The alternative hypothesis $H_a$ holds the suspected or hoped-for condition. Together the two cover every possible value of the parameter.
• Six steps: state the hypotheses → identify the test statistic and its distribution → specify the significance level → state the decision rule → collect data and calculate → decide.
• The only outcomes are reject $H_0$ or fail to reject $H_0$. A test never proves the null.