Final answer:
The most useful information in evaluating the professor's argument about the advertising campaign's success is whether the company increased spending on other forms of marketing at the time of the campaign.
Step-by-step explanation:
At the time of the campaign, did the company significantly increase spending on other forms of marketing? This information would help determine if the sales increase was solely due to the subway posters or if other marketing efforts also played a substantial role.
When analyzing the effectiveness of an advertising campaign, it is crucial to consider various elements that could have influenced the outcome. The professor's argument posits that the subway poster campaign was the driving force behind increased sales and market share. To critically evaluate this assertion, one must establish whether there were additional marketing strategies implemented concurrently that may have contributed to the success. If the company had amplified its marketing budget in other areas, this could confound the impact of the subway posters alone. It is also essential to assess the overall market conditions, such as demand elasticity and competitive landscape, during the campaign period. These factors are vital in understanding to what degree the advertising efforts shaped the consumer purchasing behavior and the company's subsequent profitability.