Internal validity refers to the degree of claim of the existence of cause and effect relationship between certain dependent and independent variables in a research study. External validity, on the other hand, refers to the inferential process that tries to establish whether it is possible for a researcher to generalize the findings of a research study basing on the settings, outcomes, times and the people considered in the experiments. However, there are factors that might make a researcher fail in the generalizations as well as in the results obtained in the attempt to establish the existence of a cause and effect relationship.
Threats to internal validity
These are extraneous variables that have the potential to confound the outcomes of a research study. They include history, maturation, instrumentation, testing, regression artifact, attrition, and selection as well as additive and interactive effects. History is any happening that can change the outcomes of the study. Maturation is the adjustment that takes place in an individual’s internal conditions due to the passage of time. Regression artifact is the behavior of extreme scores to adjust towards the mean score on a number of repeated tests .
Threats to external validity
They include the experimenter effects, effects of the experimental set up, effects of testing, specificity of variables, interferences due to multiple treatments and selection treatment interference. Experimenter effects refer to the chances of the researcher unintentionally affecting the participants’ performance in a study. When a pretest affects the responses obtained from the participants in a study this entails the effects of testing. The experimental arrangement may be affected by the participants’ knowledge that they are being studied and thus their responses may be different from what it would have been had they not known. Specificity of variables entails the degree at which variables have been defined in the study.
Conclusion
Extraneous variables that may make a research study’s outcome not present a cause and effect relationship between variables or make a researcher fail to make correct generalizations are what in research are referred to as threats. These affect both internal and external validity of a research study and should be taken into consideration at all times.
Works Cited
Christensen, L. B., Johnson, R. B., & Turner, L. (2011). Research Methods, Design, and Analysis. New Jersey: Prentice Hall .
