After several years of declining product sales, the online nutrition site NutriShake revamped its marketing strategy. Before this change, NutriShake was focused on search engine optimization strategies to boost its rankings in search results on a big interet search engine in order to get more traffic. The new marketing strategy attempted to penetrate further into customers' referral networks by making use of Pay-per-Click ads on a business social network. After the marketing strategy shift, revenue from product sales increased.
In assessing whether the improvement in product sales can properly be attributed to the marketing strategy change, it would be most helpful to find out which of the following?