system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does a company know if their TV commercial has been successful?

It seems like companies spend so much money on TV commercials. But how do they know if a commercial has been successful or not?
gpt
It depends.

Some commercials that have phone numbers use a special one just for the commercial.  Thus, any calls you get to that number are attributable directly to the commercial

For others, they will look at purchase behavior before and after the commercial airs.  If it goes up, it can be assumed to be due to the commercial

Sometimes they air commercials in specific markets.  Like the previous example, if a market with the commercial spikes, it's probably due to the commercial.