Final answer:
Internal validity deals with how well a study is conducted within its own context, ensuring that the results are due to the experimental conditions, not other factors. External validity refers to the applicability of study results to other contexts outside of the original study. Both concepts assess different aspects of a study's overall validity.
Step-by-step explanation:
The main difference between internal validity and external validity relates to whether the results of a study are trustworthy and accurate within the context of the study itself (internal validity) or whether those results can be generalized to other contexts outside of the study (external validity).
Internal validity refers to the extent to which the design and conduct of a study allow for a clear cause-effect relationship between the variables being studied. It dictates whether the experimental treatments/conditions really caused the observed effects, by ruling out alternative explanations. This involves considering factors such as control groups, avoidance of bias, and proper operational definitions of variables.
On the other hand, external validity concerns the degree to which a study's findings can be applied to other people, settings, times, measures, and characteristics than those specifically studied. It asks if the study's results serve as a reliable foundation for making inferences about other groups or situations. External validity is challenged by specific attributes of the study's sample, the uniqueness of the experimental conditions, and other situational variables.