An аrticle published оn Nаtiоnаl Public Radiо's website in 2012 discussed the recent advances in genome sequencing and offered an opt‑in poll. The question asked was, "Would you have your genome sequenced if you could afford it?" The poll stayed open for two weeks, during which time 6627 clicks were received (5398 for yes, 656 for undecided, and 573 for no). What type of sample is used in this online poll?