A student study at the University of Cambridge concluded that it takes 3,481 licks to get to the center of a Tootsie Pop.[7] Another study by Purdue University concluded that it takes an average of 364 licks to get to the center of a Tootsie Pop using a “licking machine”, while it takes an average of 252 licks when tried by 20 volunteers. Yet another study by the University of Michigan concluded that it takes 411 licks to get to the center of a Tootsie Pop. A 1996 study by undergraduate students at Swarthmore College concluded that it takes a median of 144 licks (range 70-222) to get to the center of a Tootsie Pop.[8] Harvard Grad students created a rotating mechanical tongue and concluded 317 licks.
-- Wikipedia, on the reproducibility of scientific results