To give you a quick guide as to what matters here...(1) Internal and external validity are the most important since they tie directly to the fundamental question of whether your study really works. (2...To give you a quick guide as to what matters here...(1) Internal and external validity are the most important since they tie directly to the fundamental question of whether your study really works. (2) Construct validity asks whether you’re measuring what you think you are. (3) Face validity isn’t terribly important except insofar as you care about “appearances”. (4) Ecological validity is a special case of face validity that corresponds to a kind of appearance that you might care about a lot.
