External Validitity

External Validity In dealing with the statement, “It is not possible to know whether a research finding will generalize to all populations of individuals.” behavioral scientists would like to use every possible variation of an independent variable, however, in most cases, it is not feasible. The cost and time would become too extravagant; (www.experiment-resources.com) therefore a group would be chosen to reflect the whole population. For example, if a researcher were conducting a study on how many teenagers get run away between the ages of 14-16, the ideal study would be of all teenagers between the ages of 14-16. That would be a difficult task, so a group of teenagers would be selected to represent that particular age group. The group would be considered a generalized part of the larger group. (Stangor, 2011) The main function of external validity is the process of generalization, verifying whether the results complied from a small sample group can be concurrent enough to make predictions about the entire population. In 1966, Campbell and Stanley proposed the commonly accepted definition of external validity. (www.experiment-resources.com) “External validity asks the question of generalizability: To what populations, settings, treatment variables, and measurement variables can this effect be generalized? (www.experiment-resources.com) usually, external validity is split into two distinct types, population validity and ecological validity, both are essential in determining the strength within an experimental design. There are four different types of replications. 1. Exact replications; repeating a previous research design as exactly as possible. (Stangor, 2011) Ex: A researcher designs a study on kindergarten behavior the first day of school. Another researcher performs the same design experiment at another school, replicating