Imagine that a retail manager has two different endcap displays in the store $-$ one in Aisle $2$ and one in Aisle $12-$ and would like to determine which endcap display is more effective $($i$.$e$.,$ sells more products$).$ Which of the following would you recommend the manager do$?$

Note: and endcap is a display shelf or area located at the end of an aisle. The manager is interested in establishing a causal relationship.