An advertising agency has been doing work for a client selling widgets. The three-month campaign has produced a low correlation between advertising expenditures and sales for its client. Hence, the client is considering firing the ad agency. The ad agency counters that consumer sales are not a fair assessment of the effectiveness of the ad campaign after only three months. They counter with an analysis of advertising expenditures in relation to number of requests for information about the widgets; number of distributors stocking widgets; and number of retailers requesting shipments of widgets. The ad agency has a database with such information. What kind of analysis would best assist the ad agency in making their case for the effectiveness of their ad campaign?