Which of the following hypotheses indicate an association in a research study?

The hypothesis indicating an association in a research study is one that implies a relationship or connection between two variables. In this context, the correct option suggests that racial disparities are present in how effective treatments are among different racial groups. This implies an exploration of how treatment effectiveness varies depending on racial background, which establishes an association that can be studied, measured, and analyzed.

The focus of the statement on disparities indicates a consideration of differences in outcomes, which fits the definition of an association as it posits that the outcome (treatment effectiveness) is influenced by a demographic variable (race).

Other options either present a specific cause-and-effect assumption, a null hypothesis indicating no effect, or comparison results without directly suggesting an association. Recognizing the nuances in wording helps clarify the underlying relationships that each statement implies.