focus group

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A small group selected from a wider population and sampled, as by open discussion, for its members' opinions about or emotional response to a particular subject or area, used especially in market research or political analysis.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A group of people, sampled from a larger population, interviewed in open session for market research or political analysis