Internal and external validity are important concepts in training evaluation, as they prove that its results are meaningful and relevant. Threats to validity are the factors that might affect the level of believability of the study outcomes and the extent of their generalization. Internal validity is an important featur as it provides the necessary confidence that the findings of the evaluation are the results of the training program, and not other reasons. Internal threats to validity are related to three main characteristics, including the company, persons in the evaluation study (maturation, mortality and initial group discrepancy), and outcome measures (instrumentation, testing, and regression towards the mean).
Threats to external validity are associated with the participants’s reaction to being included in the study. Additionally, they presuppose the effects of different types of training. The most common risks in this category are the reaction to pretest or evaluation, the interaction of methods, as well as the interaction of training and selection. While the evaluation does not involve all the people who have completed the program, it is complicated to predict its effectiveness for other groups.
Considering training evaluations in the radiology department, it is essential to pay attention to several threats to validity. Firstly, performing the study within a single hospital or care center restricts the generalizability of the findings. Secondly, one month or year review may provide a limited sample size. Thirdly, medical records and similar clinical data sources are not designed for research, which may introduce more threats to validity. Finally, there is no information about the physiological parameters of the patient before and during radiation therapy. Nevertheless, despite all the internal and external threats to validity, the study is necessary as it justifies the prospective researches in the area and provides essential information on the case.