Psychological Research Descriptive and Inferential Statistics

Descriptive statistics is an style of analysis that is used when wanting to describe the entire population under study. But the population studied must be small enough to include every case, or each subject. ("Definition") On the other hand, inferential statistics also studies a population, but the purpose is to expand the results to include a much larger population in general. (Healey) In descriptive statistics, the results can be used to make conclusions about the population studied, and only that particular population. While inferential statistics allows a researcher to make conclusions about larger groups based on the results of the study of one particular group.

Descriptive statistics can be used when studying a population, such as one particular class in a school, or one group of workers, and the results are to be used to draw conclusions from only that group. For example, the study may draw conclusion about girls in one class as compared to girls in another. But inferential statistics can be used when studying a population that is representative of a much larger group, for instance, using the results of a study of one class in order to study students in general. It is important that the study be constructed in such a way as to only draw conclusions that the results will allow one to make, and not more. For instance, studying people in one particular shopping mall will not allow one to claim that the result can be applied to all people at all shopping malls.

2. Case study Method and Single-subject Experimental Design

When studying groups of subjects there are two approaches a researcher can take: the case study method, and the single-subject design. While both deal with groups of subjects, and study individuals within those groups,...

research design," creates a base-line by which the individual subjects are compared. More over, the base-line is created by the subjects themselves, being observed in a "normal" condition. This result is then compared to the subject's reactions during the experiment to draw conclusion about the subjects. This method is particularly useful when testing the introduction of a new variable to the subjects and seeing what their reaction is.
Another method is called the case-study method and also studies individuals, or groups, within a population, but this method does not create a base-line with which to study the reactions of the subjects. Instead, the case-study method simply studies the subjects in order to draw conclusions about the subjects and their reactions. Case-study methods are not meant to draw general conclusions but deal mainly with individual cases. For instance, a case-study could involve one patient, and their behavior before and after some event. While the conclusions of the study may be limited to the individual involved in the case, these studies serve as good examples and when many are taken together, can serve to be the basis of another kind of study called a quasi-experiment. By connecting the results with another study, it may then be possible to draw larger conclusions.

3. True Experiments

When performing psychological experiments, one can undertake what is known as a "true experiment." This involves a very specific number of criteria, including sample groups that must be assigned randomly, a viable control group, and there can be only one variable manipulated and tested. These types of experiments usually involve two groups of subjects, one that is a control group, and one group that is the focus of the test. A variable is then tested…