What threats to internal validity exist in this study?
Validity Challenge Exercise Textbook: Chapters 5, 6 and 7 Christensen, L.B., Burke Johnson, R., & Turner, L.A. (2014) Research methods, design, and analysis (12th ed.). Upper Saddle River, NJ: Pearson. Validity Challenge Exercise: Assume that you wanted to find out if patient education promotes physical recovery among surgical patients in hospitals. You hypothesize that it does, and that patients who had more information recovered faster. To test this hypothesis, you selected patients who had elected to undergo plastic surgery to receive a face-lift to remove sagging skin and wrinkles on their face (i.e., purely cosmetic in nature). The first ten patients to request the plastic surgery were given a brief educational course by several nurses consisting of a tour of the hospital and a lecture on some basic facts about surgery. The next ten patients to request the surgery were given a group of photographs of former patients who had received a face-lift. All patients received the same plastic surgery. Prior to and after the surgery, the nurses had all twenty patients rate how they felt each day for fourteen days, and following surgery they counted the number of pain pills that the patients took to control pain. They also asked the patients to record the length of time it took them to resume normal daily activities. Statistical analysis comparing the two groups of patients revealed that they differed significantly in the number of pain pills taken, length of recovery time, and ratings of how they felt. Patients who received the educational tour felt better, resumed normal daily activities sooner and required fewer pain pills. The investigators concluded that hospitals should provide patients with education prior to surgery because the patient education had significant benefits for the patients. Use the passage above to answer the following questions in a one to two page paper: i. What type of sampling method was used? ii. What threats to internal validity exist in this study? iii. What threats to construct validity exist in this study? iv. What threats to external validity exist in this study?