a researcher announces that he will be conducting an experim

a researcher announces that he will be conducting an experiment to investigate the detrimental effects of sensory deprivation on perceptual motor coordination. The first 40 students who sign up for the study are assigned to the experimental group, and the next 40 who sign up serve as the control group. The researcher supervises all aspects of the study\'s execution. Experimental subjects spend two hours in a sensory deprivation chamber, where sensory stimulation is minimal. Control subjects spend 2 hours in a waiting room that contains magazines and a tv. All subjects then perform 10 1-minute trials on a pursuit-rotor task that requires them to try and keep a stylus on a tiny rotating target. The dependent variable is their average score on the pursuit rotor task. What are the methodological flaws of this study?

Solution

There are 2 flaws that I could find, there may be more.

1) Subjects should be assigned randomly to control and treatment, rather than taking them sequentially. There might be some relationship between sign up time and dependent variable, that could affect our results.

2) Subjects know whether they are in control/treatment group. This may create a placebo/nocebo effect and could change our results. Ideally, subject should not even be able to guess whether they are in conrol or in treatment group. This means that even in sensory depreivation chamber, there should have been magazines/TV etc, but with less activating programs in them.