Which of the following represents a key function of ratings in broadcasting?

The key function of ratings in broadcasting is to measure the percentage of households that own televisions and are tuned into a particular program or channel. This data is critical for broadcasters, as it informs them about the viewership levels and helps gauge the popularity of their content. By understanding how many households are engaged with a show, networks can make informed decisions regarding programming, scheduling, and advertising strategies.

Although monitoring advertising costs, assuring program diversity, and determining viewer demographics are integral components of the broadcasting ecosystem, they do not capture the primary function of ratings. Ratings primarily focus on quantifying audience size and engagement, which serves as a foundational metric for most broadcasting and advertising decisions.