Any research based study starts with a research objective, and that objective comes out from a research gap in any context. The research gap comes out of the careful scrutiny of the literature on several contexts, and when the researcher finds out that a particular piece of study is missing in any particular context, a research gap is established. Now in order to fill up that particular research gap, a research based study has to be carried out, and that is how a particular research based study is started.

However, in most of the cases, researchers simply start off with a research based study, without validating the research gap, and that is the reason, those studies fail to gain significance among the community of researchers. Those studies are nothing but a mere replication of any previous studies, with a mere extension in the dataset, or a change in methodology, and as soon as those studies come to conclusions, which have already been established by previous researchers, those studies lose their significance automatically. That is why literature review has to be carried out extensively using Meta analysis process. This process is actually a top-down approach to find the research gap, and it is considered as one of the best ways to establish a research gap. In this process, based on the theme of the study, nearly all of the pieces of literature are reviewed, and their objectives, spans of study, data, methodologies, and results are recorded. In this process, researcher can observe a clear picture of the existing body of knowledge regarding that scope of study, and therefore, establishing a clear research gap becomes easier. One of the major advantages of this analysis is that the gap established by this process can hardly go wrong, as this analysis is the most extensive one considering literature review. For more information about various aspects of Meta analysis, kindly browse through the pages of www.scoringhigh.co.uk.

The purpose of the control group in an experiment is to control the various possible effects of rival explaining a causal finding. We may then be in a position to take actual view that the study is valid internally.  The random assignment of subjects to the control and experimental groups and the presence of a control group enable to eliminate rival explanations and eliminate internal validity threats.

The threats include the following:

• The threat of testing implies the possibility that subjects may become sensitive to the objectives of the experiment.
• The threat of history refers to the possibility that events in the experimental environment may have led to the changes.
• The threat of maturation says that people change and the ways they change have implications for the dependent variable
• Another threat is that if differences exist between the two groups because of selection by a non random process, there would be variations between the control group and experimental groups. This could be attributed to pre-existing differences in their membership.
• A direction of causality would be there if there is the notion of an independent and dependent variable. There may be situations when the temporal sequence becomes unclear which makes it difficult to establish which variable affects the other. The presence of a control group helps to clear this feature.