What does a null hypothesis state about variables or groups measured?

The choice indicating that the null hypothesis states there is no difference between the variables is accurate because the null hypothesis serves as a foundational component in statistical hypothesis testing. It posits that any observed effect or difference in data is due to chance rather than a specific relationship or effect between the groups or variables being studied.

This concept allows researchers to test their assumptions and determine whether there is enough evidence to reject the null hypothesis in favor of an alternative hypothesis, which typically suggests that a significant difference or effect does exist. By asserting that there is no difference, the null hypothesis establishes a baseline against which statistical tests can measure the strength of evidence for an alternative claim. This is central to many experimental designs and the interpretation of results in research and evaluation.