Non-equivalent groups in research can lead to which of the following?

Non-equivalent groups in research can lead to a possible confounding variable because when groups are not equivalent, any differences observed between the groups might be attributed to a variety of uncontrolled factors rather than the treatment or intervention being studied. This lack of equivalence can introduce bias, making it difficult to draw valid conclusions about causal relationships. For example, if one group has significantly different characteristics (such as age, socio-economic status, or previous experience with the subject matter) compared to another group, it becomes unclear whether the outcomes are due to the intervention itself or these underlying differences. Thus, the presence of non-equivalent groups highlights the risk of confounding variables that can obscure the true effects of the research being conducted.