Buying TV ads has often been an exercise in guesswork. Advertisers try to pick which shows are likely to attract the biggest numbers of viewers most apt to purchase their soda, sneaker or cell phone. And then they pay millions of dollars and hope for the best.

NBCUniversal hopes to improve that process with the introduction of a new tool that will use various kinds of data to identify the best TV inventory for, say, an automobile maker looking for younger buyers, or a soda maker seeking high-income female viewers. NBCU’s “Audience Targeting Platform” will use data from set-top boxes and other sources to identify the best inventory across the company’s cable and TV networks for specific advertising categories, said Linda Yaccarino, chair of NBCUniversal’s advertising sales and client partnerships.

“There is a growing and deafening demand and push for more insight as it relates to television investment,” Yaccarino said in an interview Thursday.

The offering comes as more advertisers seek alternatives to what has long been the industry standard: Nielsen’s age-and-demographic measures of viewers who watch TV in traditional fashion. With more viewers gaining access to video on mobile tablets and other digital-streaming methods, sponsors are also seeking information about viewer behavior.

The plan is also unveiled before what could be another bruising upfront market, when the U.S. TV networks try to sell the bulk of their ad inventory for the coming programming year. In 2014, only NBC among the English-language broadcasting networks was able to notch more advance commitments from advertisers. Meantime, the amount of money committed in advance fell for both overall broadcast and cable as marketers held purse strings tight and put more emphasis on digital advertising related to mobile devices and social media.

“We will be able to organize and maximize the inventory across the whole NBCU portfolio,” Yaccarino said. “We will be able to create harder working media plans for them, and be able to parse it out and put it aside and reserve it for them.”

NBCU’s announcement is timed, she said, to coincide with a period of time when advertisers start to put more thought into how they will spend ad dollars in the back half of 2015 and into 2016.

Others have attempted similar projects. In 2008, ABC offered an “Advertising Value Index” that gave marketers the ability to choose from among such criteria as income, education, attention to commercials and viewer engagement with programming to help them determine what kind of inventory to buy across the Disney network’s schedule.