In its purest form market research attempts to produce unbiased results on a scientific level. It's a tool used for everything from measuring customer satisfaction to trying to predict the next big hit product. Problems occur when the data is collected in a biased way, or the results are interrupted to suit the people who commissioned the study just to show their bosses that they did their due diligence. I can tell you from experience that the same data can be used to support any side of an argument. Focus groups are a popular way to do market research because they are fun.
Clients get to sit behind two way glass scarfing down catered food while spying on their customers.
And focus groups are the worst way to abuse market research. Focus groups involve gathering a room full of customers or product users and leading them through a moderated discussion. Having a group involved is supposed to make the individuals work with each other to release ideas and thoughts they might not have thought of in a one on one situation. Unfortunately in some groups certain individuals dominate and the other tend to follow along with the group. In other cases individuals are of the type that they don't want to offend anyone, including the company sponsoring the study, so they only give nice, polite and positive comments.