What is External Validity?

, , Comments Off on What is External Validity?

External validity is a type of validity, which refers to how likely it is that the results that researchers obtained from a small sample size can be extended to the whole population across different times. This is considered to be the most difficult one to achieve among the different types of validity. Once a research has displayed a low level of external validity, it is more likely that the results of the study will not be regarded as significant.

According to Campbell and Stanley, external validity is about generalizability. They say that this concept asks the question: To what kind of settings and population can the results of this study be generalized? Their proposed definition which was made in 1966 is still the most widely accepted one up to this day.

External validity is one of the reasons for a little tension between research psychologists and psychologists in the clinical field. Some psychologists who practice in the clinical field claims that the research psychologists, who spend their time testing humans and animals in their laboratories, produce results in their studies which have no external validity. According to these clinical psychologists, the conditions and setting in the laboratories do not adequately resemble those of the real outside world and therefore cannot be generalized. Furthermore, clinical psychologists assert that these studies also fail to take into account each person’s individuality and the complexity of the human mind.

There are two types of external validity namely, population validity and ecological validity. Normally, studies conducted by research psychologists have high levels of population validity because the groups are randomly selected and large sample sizes are used, in order to have more meaningful statistical results. However, the ecological validity is low because of the artificial nature of this type of psychology.

Through statistical analysis, research psychologists are able to find trends, make generalizations, and also predict behaviors. However, there are cases wherein some people deviate from these generalizations. Clinical psychologists then end up trying to pick up these pieces and study these individuals.

Tea Time Quiz

[forminator_poll id="23176"]