Subjects' simplification of rules for estimating money saved when buying a specified quantity of a cheaper product compared with a more expensive one

Abstract.— Estimates of money saved, when buying a specified quantity of flowers of a cheaper kind compared with a more expensive kind, were collected from two different groups, for different quantities and combinations of prices. One group gave their estimates in 13 sec, and the other in 15 sec. The data were analysed according to four different models, all consisting of a multiplicative combination of two components, one related to the quantity to be bought and the other to the combination of prices. The estimates of both groups showed systematic deviation from the correct savings, and the estimates of the groups were best described by one simple and one more complex model respectively.