Educational psychology: master's level paper on quantitative design

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Assessment 5 Context

Quantitative Methods: Experimental and Quasi-Experimental Approaches

Experimental Research

Experimental studies compare the effect of one or more independent variables on one or more dependent variables. The independent variable, or presumed cause, is manipulated by the researcher. In this case, when a variable is manipulated or controlled by the researcher, this means the research can control whether research participants are exposed to that variable. The hallmark of experimental designs is the random assignment of participants to the levels of the independent variable. Causation can be inferred in true experimental research. Certain types of single-subject experiments can also be classified as experimental designs. As such, causal attributions can be inferred (Meltzoff, 1998).

Research questions that require an experimental approach ask questions about the causal effect of one variable on another. For example, a researcher might ask, "Does tutoring affect test scores?" Because this question asks whether tutoring (the independent variable) affects test scores (the dependent variable), it is asking about a causal relationship. This can only be answered with confidence using an experimental approach, which would require the researcher to be able to manipulate tutoring. In other words, the researcher must be able to randomly assign research participants to receive tutoring or not receive it, and compare the test scores of the two groups. If there is a statistically significant difference, the researcher is in a position to be able to conclude that tutoring caused the difference in the test scores.

Quasi-Experimental Research

Quasi-experimental research designs come in many different forms. Like experimental research, the researcher aims to compare the effect of one or more independent variables on one or more dependent variables. However, the researcher does not or cannot randomly assign participants to the comparison groups, due to ethical or logistical concerns, so cause-and-effect relationships cannot be conclusively established.

Research questions that require a quasi-experimental approach ask about group differences or differences in conditions. For example, a researcher might ask, "Is there a difference in test scores of students enrolled in different sections of the same class?" A researcher would not have assigned the students to be in one class section or another. The students either would have signed up for a course section or been assigned to a section by an advisor, guidance counselor, or registrar. Since the researcher cannot randomly assign the research participants to the class sections, a quasi-experimental approach is needed. Another example of a research question that would require a quasi-experimental approach might be "Do the test scores of students improve after they receive tutoring?" This question requires a comparison of at least two scores in one group of participants, basically a pretest and a post test. The researcher would have to collect test scores from the participants before the tutoring and after the tutoring, and compare the scores. The researcher would not be able to conclude a definitive causal relationship between the variables in either example.

It is particularly important that the researcher carefully considers the threats to validity in the interpretation of the results of quasi-experimental research designs.

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References

Meltzoff, J. (1998). Critical thinking about research: Psychology and related fields. Washington, DC: American Psychological Association.