Which of the following is a key factor in determining digital advertising effectiveness?

Cost per click is a key factor in determining digital advertising effectiveness because it directly correlates with how much an advertiser is willing to pay for user engagement with their ads. This metric measures the monetary cost incurred each time a user clicks on an ad, which indicates a level of interest and intent to learn more about the offering. A lower cost per click suggests that an ad is efficiently reaching the target audience, generating traffic, and potentially leading to conversions, which is essential for assessing the return on investment of advertising campaigns.

In contrast, other options do not typically represent standard metrics used in evaluating digital advertising effectiveness. Cost per weather, for example, is not a recognized advertising metric and does not align with common industry terms. Similarly, cost per bid is more relevant to auction-based advertising systems and illustrates the amount an advertiser is willing to pay to secure space but does not provide a clear indication of whether those bids translate into successful user interactions or conversions. Cost per branding is not as quantifiable as cost per click and would focus more on brand recognition rather than direct engagement metrics. Thus, cost per click stands out as the most relevant and actionable measure for effectiveness in digital advertising.