Recommend and describe a specific experimental design to select the most effective social media campaign. In your answer, outline the independent, dependent, and possible extraneous variables involved, as well as the recommended experimental setting.

$(1)$ The first focuses on exclusive member discounts and $(2)$ The second focuses on the sense of community among members. Due to time and budget constraints, only one social media campaign can be implemented, so the client would like to conduct an experiment to determine which one will be most effective.