Clinical research: External validity Vs. Internal validity

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24 Jul 2016 - General

The ultimate purpose of a clinical research is to draw inferences form the result of the particular study, about the nature of universe around it. By doing a clinical research, we hope that the truth in the clinical study will infer the truth in the universe. There are 2 factors involved in this which are the internal validity and external validity of the study. Internal validity means that the degree of the investigators draws correct result from what was actually occured in the clinical study. External Validity means the degree of those conclusion from the clincial study, can be applied to the universe/ people outside the study.There are a few errors that could be happened, and the goal is to maximize the validity of inferences of the study to generalise population. Is anyone who is familiar in designing clinical research would like to give some in-sight with regards to striking the balance between internal and external validity???

@Ziwei, bothe internal validity and external validity are the core pillar for clinical research study (inclusive of all trial designs). The concept can be a bit confusing. You have pointed of a salient point of whether “the sample in the study do represent the whole population of interested ??, and can we generalise the result from the sample group to the entire population of interested??”, and this is the rough concept of external validity. Internal validity is about the clinical study its...
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I am not good at research design however I will give my opinion, Basically it means the sample population must resemble to target population as much as possible. One way, based on the sampling model, suggests that you do a good job of drawing a sample from a population. For instance, you should use random selection, if possible, rather than a nonrandom procedure. And, once selected, you should try to assure that the respondents participate in your study and that you keep your dropout rates low. ...
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