an artificial expert system and method for determining whether to buy , sell , or hold a specific individually traded unit of publicly traded units residing in a securities or investment portfolio owned or controlled by a user , wherein the portfolio comprises of at least the trading statistics of each itu . in one embodiment , the invention provides a user with a rational basis : to sell the optimum number of itu &# 39 ; s to unload at the optimum itu sale price or buy the optimum number of itu &# 39 ; s to purchase at the optimum itu purchase price or recommend that the user neither buy nor sell any of the selected itu &# 39 ; s .