The certainty effect is a reference to the psychological effect that results from the reduction of probability from certainty to probability. This theory, posited by Kahnemann and Tversky. also gave rise to the pseudocertainty effect and the prospect theory. This theory was researched through the use of progressive questions regarding choices between various probabilities of winning.
For example, "If given the choice between a 90% chance of winning $20, or a 50% chance of winning $60, which would you choose?" These types of questions study attitudes about gambling and faith about luck in regards to chances of winning.