What online activity is worth the effort and actually leads to sales? Banner ads, Facebook likes, links to the time you were on public radio? - 

DiamondCandles is a North Carolina-based online business which sells eco-friendly candles that come with a surprise ring inside.

"It's kind of like a Cracker Jack box," says CEO Justin Winters.

Depending on your luck, you can win a ring worth anywhere from $10 to $5,000.

DiamondCandles attracts customers mostly over the web. But what online activity actually leads to candle sales? Banner ads, Facebook "likes", links to the time you were on public radio?

To make sense of it all, DiamondCandles turned to a New York startup called SumAll, which has come up with a way to let clients look under the hood and see the stats on what online action caused what online reaction.

SumAll's founder Dane Atkinson says big Internet companies have a mountain of data on this, but getting the information and then parsing it is tricky.

"It's terrifying how much data they actually collect on your behalf, but they don't show it back to you," says Atkinson. "Google is actually one of the better tools out there, but many of them keep 90 percent of the information in the cloud, invisible to you."

That's where SumAll steps in. The company seeks out all of its client's information and, as their name suggests, sums it up in easy-to-understand stats and figures. So what's a Facebook "like" worth?

"On average across all our customers, a 'like' is worth a little bit under $1, an Instagram photo is worth a lot more, a post can be worth hundreds of dollars," says Atkinson.

To hear more about the value of social media advertising, click on the audio player above.

Follow David Brancaccio at @DavidBrancaccio