The null hypothesis is a claim about a:
It is needed to explain about the null hypothesis.
The hypothesis, which is pre assumed as true, tentatively settled up and tested to check the plausible rejection of it, is called as the null hypothesis. On the other hand, the hypothesis that opposes or contradicts or the null hypothesis is the called as alternative hypothesis.
The null hypothesis is denoted by H_{0} and the alternative hypothesis is usually denoted by H_{1} (or H_{a}).
Hypothesis always state a statement regarding a value of parameter, as it is needed to test the claim regarding the particular value of the parameter using the help of sample statistics.
That is, the null hypothesis is a claim about a population parameter.