Question

How methods of data collection and analysis jeopardise external validity ?

Answer 1

External validity refers to the degree to which the results of a sample study/ data collection/ experiment can be held to be true or generalised to and across individuals, settings, and times. But, there are some factors which jeopardise the generalisation; they are:

Reactive or interaction effect of testing: A pre-test might increase or decrease a subject's sensitivity or responsiveness to the experimental variable such that the results cannot be generalized.

Interaction effects of selection biases and the experimental variable: The results of an experiment in which teaching method is the experimental treatment used with a class of low achievers, do not generalize to heterogeneous ability students.

Reactive effects of experimental arrangements: An effect when the subjects know that they are participating in an experiment, where the result may vary upon subjects being exposed to it in non - experimental settings.

Multiple treatment interference: It happens when the effects of earlier treatments are not erasable. When multiple treatments are given to the same subjects, it is difficult to control the effects of prior treatments.