Internal and External validity cogitate that whether or not the results of a study are meaningful. Internal validity is related to the structure of the study whereas external validity is related to how relevant is the findings of the study to the real world. Internal validity is a prerequisite to external validity, trade-off or tension between internal and external validity appear upon the analysis.
When people suffer from -panic- disorder, they often feel intense fear that something horrible is about to happen. these feelings last minutes and include heart palpitations, shortness of breath, and dizziness?
An example would be if a president were focusing one thing and the next day there is a story of bombings on tv he may be more compelled to do something about it.