Internal validity regards to the internal logic and consistency of the research. If research is seen as an argument then internal validity is about the logic and consistency of this argument. It is most clearly and narrowly defined in the quantitative context (Punch, 2013, p.323). The major threat to internal validity is history. A history threat occurs between the beginning of the treatment and the posttest. Here are other six prominent threats to internal validity: maturation or the passage of time, testing, instrumental changes, statistical regression, selection biases, and ambiguity about the direction of casual influence.
External validity threats are the wrong choice of place, people, and time. According to Creswell (2013) threats appear when the researcher goes wrong with the data and comes to incorrect conclusions. These threats arise because of the characteristics of individuals, selected for the research, the uniqueness of the setting and the timing of the experiment. …show more content…
The researchers consider a healthy control group as a highly efficient way of reducing internal threats. To mitigate external validity threats, random sampling is always desirable. Its benefits for external validity are so great. Random sampling simplifies external validity inferences and eliminates possible interactions between the casual relationship and the class of persons (Creswell, 2013, p. 155). Proximal similarity theory will also help mitigate threats. Needless to say, internal and external validity threats have an impact on the results in a negative way, but they can be mitigated to get reliable