Problem
Dr. maya is testing the effects of a new allergy drug, Drug r He gathers a sample of individuals with severe allergy symptoms by contacting allergist offices. Dr. maya then measures the severity of their symptoms using the Allergy Checklist of Holistic Objective Operations, a well-established and highly researched self-report questionnaire with high validity and reliability. Each subject receives one week's worth of the new medication and takes one tablet each day as directed. All subjects return to retake the ACHOO. The average symptom severity in the sample has been reduced significantly.
• List which of the threats to internal validity the doctor should be concerned about in this study and describe each of them.
• Which of these is the single most concerning of these threats and Describe why?