Which statement describes the purpose of a null hypothesis?

The purpose of a null hypothesis is to serve as a default position to test against in a statistical analysis. More specifically, the null hypothesis posits that there is no effect or no relationship between the variables being studied. This baseline assumption is essential because it allows for the establishment of a comparison point during hypothesis testing. When researchers conduct a test, they look for evidence to either reject the null hypothesis or fail to reject it based on the collected data.

This framework is crucial in statistics as it helps to determine whether any observed differences or relationships in the data are statistically significant or could be attributed to random chance. A null hypothesis creates a structured way to approach the inquiry, facilitating clearer conclusions from the analysis.

In contrast, the other choices suggest alternative roles or misconceptions about the null hypothesis. For example, proposing a relationship or effect is characteristic of an alternative hypothesis, not a null hypothesis. Similarly, confirming previous findings is a separate analytical goal that does not align with the foundational role of the null hypothesis in hypothesis testing.