If two independent studies investigating the same phenomenon arrive at contradictory conclusions, but both used appropriate statistical methods, what is the MOST likely explanation for this discrepancy?

If two independent studies investigating the same phenomenon arrive at contradictory conclusions, but both used appropriate statistical methods, the most likely explanation for this discrepancy is differences in the study populations or samples. Even with appropriate statistical methods, variations in the characteristics of the groups being studied can lead to differing results. These differences might include demographics, pre-existing conditions, environmental factors, or other variables that were not fully controlled or accounted for in the study design. Although both studies may have employed sound methodologies, the inherent variability within and between populations can result in conflicting findings. Publication bias (where studies with statistically significant results are more likely to be published) or small sample sizes in either study could also contribute, but differences in the underlying populations studied are the most probable explanation given appropriate statistical methods were used in both.