Internal and External Validity

Validity, as we discussed in our lesson on measurement, is the extent to which a measurement is free from sampling errors and systematic errors. With experiments there are two kinds of validity that concern marketing researchers: Internal Validity and External Validity.

Internal Validity: Internal Validity refers to the extent to which variations in the response or dependent variable are due to changes in the independent or predictor variable. Laboratory experiments tend to have higher internal validity and experiments conducted in the field—the marketplace—because the laboratory situation makes in easier to isolate the impact of other variables on the dependent variable.

External Validity: External Validity is to which the extent the causal relationship measured in an experiment can be generalized to the population. Field experiments offer higher levels of external validity than laboratory experiments.

 

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