Which of the following is a concern for a researcher conducting a cross-sectional study?

While it is true that cross-sectional studies primarily show associations rather than causal relationships, this concern is not specific to the design of the study itself but rather a general limitation applicable to many research methods. Establishing correlation is a broader issue that does not uniquely pertain to the challenges of cross-sectional studies.

Attrition bias refers to the loss of participants over time, which is more relevant in longitudinal studies where participants are followed over an extended period. Cross-sectional studies collect data at one time point, thus minimizing concerns regarding participant dropout and its potential impact on results.

Practice effects generally refer to improvements in performance due to repeated testing, which is a concern primarily in longitudinal studies. Since cross-sectional studies gather data at a single point in time, this bias is unlikely to influence the results significantly.

Changing instruments can introduce variability and is more relevant in longitudinal studies where multiple measurements are taken. In a cross-sectional study, instruments are typically applied uniformly at one time point, making this concern less applicable.