Identify the Confounds and Threats to Internal Validity. For the following four studies (A, B, C, and D) identify the independent and dependent variables. Identify and discuss the threats to internal validity. How would you improve these studies?
(A) Researchers want to test whether mountain climbing will increase strength, perceived competence, and immune system functioning in juvenile delinquents. A one-week mountain climbing expedition to Mount Whitney is planned. Twenty-five male adolescents in a Los Angeles County rehabilitation facility have volunteered for the project. Twenty-five male adolescents from a San Diego County rehabilitation facility will be randomly selected to serve as a control group. The project will begin August 8 and end August 15. All subjects will be tested daily at 5 p.m. on: (1) strength as measured using a dynamometer which is a valid measure of grip strength, (2) perceived competence as measured by a questionnaire, and (3) immune system functioning as measured by the volume of t-cells in blood samples.
(B) The infamous sleep researcher, R. U. Asleep, wanted to study the effects of REM (Rapid Eye Movement) sleep deprivation on maze running ability. The experimental group consisted of five male hamsters all from the same litter to control for age, gender and genetics. The control group consisted of five male hamsters from another litter. Baseline maze-running ability was established for both experimental and control groups. The experimenter set up small individual running wheels, which were fully enclosed to control for hamster location. Hamsters in the experimental group slept inside the wheels to adapt to the apparatus. The experimental group was deprived of REM sleep for 120 hours in the following manner. REM sleep was detected by using electromyography. At the onset of REM in the experimental condition the running wheel would begin to turn in a clockwise motion and force the hamster to wake up and run. Maze-running ability was tested every twenty-four hours for all subjects.
(C) The local school district wants to compare three anti-smoking programs used at the sixth grade level. The superintendent makes the following assignments based upon his own best judgment. School 1 will view a film program that features prominent celebrities promoting the anti-smoking message. School 2 will listen to guest lecturers who are suffering from lung cancer in an organized health awareness assembly. School 3 will receive training in a workshop on resisting peer pressure and assertiveness techniques during physical education classes. Each condition will require about one hour of school time. Each student that participates must have written permission from the parent. All students are pretested and posttested, using a Smoking Behavior and Interest Inventory.
(D) Researchers want to compare different methods of teen sex-education and intervention. Intermediate schools and high schools located in the northeast region of Fresno will implement a social inoculation training curriculum which involves role-playing and discussions about real-life sexual dilemmas and pressures that adolescents typically confront. Intermediate school and high schools located in the south region of town will institute a program that involves classes hosting guest speakers who relay personal accounts of their experiences. These speakers would include a person suffering from AIDS, a teenage mother, a teenager who contracted a sexually transmitted disease, a teenager who gave birth to an infant suffering the effects of fetal alcohol syndrome, etc. All of the other intermediate and high schools in the Fresno school district will only have group discussions about sexuality, facilitated by a science teacher. All of the adolescents will be administered a survey, entitled Sexual Attitudes and Behavior Inventory, both before and after they participate in their assigned curriculum.