Which symbol denotes a null hypothesis?

The symbol that denotes a null hypothesis is H0. The null hypothesis is a fundamental concept in statistics, particularly in hypothesis testing, where it represents a default position that there is no effect or no difference in the population being studied. It serves as a starting point for statistical analysis, with the aim of being tested and potentially rejected in favor of an alternative hypothesis.

In contrast, the alternative hypothesis, commonly denoted as Ha, represents the hypothesis that there is an effect or a difference. The other symbols, such as Hn and Hr, are not standard notations used in hypothesis testing and thus do not convey the same meaning as H0. Thus, H0 is recognized universally within the field of statistics as the appropriate symbol for the null hypothesis, making it the correct choice.