snowball sample
n.— «Researchers pursue what is called a “snowball sample,” seeking out workers who then recruit their friends in a process they liken to a chain letter, or to the “six degrees of separation” theory of connectedness. A mathematical formula is applied to the sample like a “corrective lens,” Professor Heckathorn explained, to obtain a sample that is “theoretically independent of its nonrandom starting points.”» —“In Challenge to Survey Low-Wage Workers, Researchers Pursue ’Snowball Sample'” by Sam Roberts New York Times Apr. 15, 2006. (source: Double-Tongued Dictionary)
Further reading
Twice a day the River Thames recedes, revealing a muddy shoreline. Hobbyists known as mudlarks stroll the surface searching for objects that have found their way into the river over the centuries, everything from ancient Roman jewelry to modern...
Sean in Oneonta, New York, says that when he was growing up in New Jersey, his family would pile in the car and set off on a surprise adventure, whether a short distance or long, and the kids would be told only that they were going on Buxtehude...