Please discuss the advantages and disadvantages of an experimental design with respect to internal and external validity.

What will be an ideal response?

Statistical theory tells us that experiments conducted properly can lead to valid inferences about causality. In this context, however, validity has a particular meaning, namely, that the manipulation of the experimental or independent (delete extra spaces) variable itself, and not some other variable, influenced the dependent variable. This kind of validity is known as internal validity, which means the research procedure demonstrated a true cause-and-effect relationship that was not created by spurious factors. Social scientists generally believe that a randomized controlled experiment has strong internal validity. Several things, however, can affect internal validity, including history, maturation, testing with a pre and post-test, selection bias, experimental mortality, instrument decay, or demand characteristics. While each of these factors represents a potential pit fall for an experiment when it comes to internal validity, the experimental design generally has very good internal validity. But, even if we devised the most rigorous laboratory experiment possible, some readers still might not be convinced that we have found a cause-and-effect relationship that applies to the real world. The concern is a lack of external validity, the extent to which the results of an experiment can be generalized across populations, times, and settings. The most common external validity objection is that experimental results may not be found using a different population.