What factor can negatively impact internal validity?

Internal validity refers to the extent to which a study accurately establishes a cause-and-effect relationship between the independent and dependent variables. When extraneous variables are present in a study, they can introduce alternative explanations for the observed results, thus undermining the internal validity. Extraneous variables are any variables other than the independent variable that may affect the dependent variable. If these variables are not adequately controlled, they may influence the outcomes of the experiment, leading to confounding results. This diminishes confidence that changes in the dependent variable are solely due to manipulation of the independent variable.

In contrast, controlled variables ensure that conditions remain constant and do not influence the outcome, random sampling methods help in obtaining a representative sample and reduce bias, and standardized testing conditions provide consistency across different testing environments. All these contribute positively to maintaining internal validity rather than impacting it negatively.