The null hypothesis (H0) is a statement that posits no effect, no difference, or no relationship between variables in a statistical test. It serves as the baseline assumption that researchers seek to test against, and the goal of hypothesis testing is to determine whether there is enough evidence to reject the null hypothesis in favor of an alternative hypothesis (H1) that suggests an effect or difference exists.

The null hypothesis (H0) is a statement in statistical hypothesis testing that suggests there is no effect, no difference, or no relationship between variables in a population. It serves as the default or starting assumption that any observed effect in the sample data is due to random chance. 

The null hypothesis (H0) is a statement of "no effect" or "no difference." It is the default assumption that there is no significant relationship or difference between variables.