The physicist Robert L. Park questioned if mind really could influence matter then it would be easy for parapsychologists to measure such a phenomenon by using the alleged psychokinetic power to deflect a microbalance which would not require any dubious statistics but "the reason, of course, is that the microbalance stubbornly refuses to budge." Park has suggested the reason statistical studies are so popular in parapsychology is because they introduce opportunities for uncertainty and error which are used to support the biases of the experimenter. Park wrote "No proof of psychic phenomena is ever found. In spite of all the tests devised by parapsychologists like Jahn and Radin, and huge amounts of data collected over a period of many years, the results are no more convincing today than when they began their experiments."