: State the type of experiment being conducted in the following situation. Also, identify the potential threat to internal and external validity.

Procter & Gamble wants to determine if a new package design for Tide is more effective than the current design. Twelve supermarkets are randomly selected in Chicago. In six of them, randomly selected, Tide is sold in the new packaging. In the other six, the detergent is sold in the old package. Sales for both groups of supermarkets are monitored for three months.