Review of validities

A local merchant claims that when the weather changes (e.g., as we go from warmer summer weather to cooler fall weather), her customers become insecure and that causes them to buy more clothes.

A study supporting the merchant's claim would NOT need to have

If the claim was only that changing weather causes her customers to buy more clothes, a study supporting that claim would need to have

Suppose the merchant established that, in her local area, her claim was correct. What would be needed to establish the external validity of that conclusion?

Any study supporting her original claim would probably NOT have internal validity because any such study would NOT have

If buying clothes is a good measure of feeling insecure, a study comparing the merchant's sales with the weather might have good

If people were buying new clothes when fall arrived because they were doing their back-to-school shopping, the conclusion that changes in weather caused people to buy clothes would lack

If people were buying new clothes when seasons changed because they were buying clothes that were a better match for the outside temperatures, the conclusion that changes in weather were making people buy clothes because weather changes were making people feel insecure would lack

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