Just think about any relationship for a moment. How long you've known a person is incredibly important. It's not the be-all-end-all, but it is fundamental to trust. If you've known someone for years and years and other people that you know who you already trust can vouch for that person, then you're far more likely to trust them, right? But if you've just met someone, and haven't really vetted them so to speak, how can you possibly trust them?
When running PPC ads, it's important that you keep careful track of the specific ads and keywords that you're targeting. You can do this by using the Google Analytics UTM builder to create campaign URLs that you can use to track the campaign source, the medium and any keywords or terms that you might be targeting. This way, you can determine the effectiveness of any campaign that you run and figure out the precise conversion rate.