As independent variable of the current study, the experimenter used measures of self-esteem of students. A dependent variable was an academic success/failure of students. Students` success was measured by good grades while students` failure was measured by exclusion them out of the college.
The experimenter suggested that low and high self-esteems influence the academic success and achievements of students in the college. However, she could be wrong with her final conclusions. Of course, it is possible that low self-esteem influences academic success negatively and high self-esteem influences academic success positively. However, it is also possible that low self-esteem is a consequence of failure in a college while high self-esteem is a consequence of academic success. So the experimenter could be wrong when she considered self-esteem as the cause of academic failure or success because self-esteem of participants of the study could be the result of failure or success.
This study used non-experimental design because the researcher had not possibilities to manipulate conditions of the study. We can suggest that it was correlational study used by the researcher for finding the reason of high and low college performance of students. The mistake of the author of the study was that she made wrong conclusions. As it is known correlation between two variables (in this case correlation between self-esteem and academic success) does not mean that one of these variables are the reason which causes another variable.
The hypothesis of the study, as I understood, was that chlorpromazine improves cognitive functioning of patients with schizophrenia. This hypothesis is directional one. I selected directional hypothesis because I believe and that experimenters expected the possible positive effect of chlorpromazine. If they did not, it would mean that experimenters exposed patients to drugs which could harm patients.
The design of the study was an experimental design because it used randomization, and experimenters manipulated actively experimental conditions. I think this design was appropriate for the particular situation because researchers had to examine the effect of the drug chlorpromazine on cognitive functions of schizophrenics and needed to use this drug for patients in laboratory`s conditions.
Independent variable of the study was the treatment by the drug chlorpromazine. The dependent variable was the cognitive functioning of schizophrenic patients. The dependent variable was measured by assessing the ability of patients to successfully perform the task.
Possible confound of the current experiment could be caused by the fact that patients performed similar tasks two times –after injection of Placebo and after injection of chlorpromazine. Patients performed tasks after injection of drugs a second time. It means that repetitiveness of similar tasks could influence the improving of patients` performance.
I think that it was useless to match police officers and park workers on an educational level because an educational level is unlikely to influence cancer. To match officers and park workers on age, gender and others characteristics also was unnecessary, as I believe. Also, I believe that it was wrong to compare park workers and police officers. At the same time, it could have the sense to measure such characteristics of police officers and park workers as bad habits, lifestyle characteristics, etc.
I think it would be better to obtain the information from a database about cases of cancers among police officers from different states who used radar guns and who did not use radar guns.
Also, I think it was a mistake to form comparable group randomly. For this study, as I understand, it was possible just obtained data about cases of cancers among all police officers from this and other states.
As I understood, it was non-experimental (observational) cohort study because it compared two groups of workers – those who did not use radar guns and those who were exposed to the potentially negative influence of radar guns. The problem of this type of study is that it could study only those individuals who work at the current point of time. In this case, we do not know if participants of the study were former workers or only current police officers and park workers (Checkoway, Pearce & Kriebel, 2007).
But if it was only current workers and officers who participated in the study it was a mistake, because it means that the study did not consider cases of cancer among former workers. Also, it is known that a cross-sectional design of a study is not appropriate one when researchers try to investigate such diseases as cancer.
References
Checkoway, H., Pearce, N. & Kriebel, D. (2007). Selecting appropriate study designs to address specific research questions in occupational epidemiology. Occupational and environmental medicine, 64(9), 633-638.
Knight, K. L. (2010). Study/experimental/research design: much more than statistics. Journal of athletic training, 45(1), 98-100.
