Abstract
It is difficult to precisely describe all aspects of such complicated sysetms as economic or social system in which human factors are included.A fuzzy funciton based on fuzzy set theory can be effectively employed to express the vegueness of phenomena in these systems.In this paper, vague or possibilistic data observed are defined as fuzzy numbers which are fuzzy sets in a real line, and a fuzzy time-series model is constructed by using a fuzzy function of time whose parameters are fuzzy numbers for expressing a trend in fuzzy data in time series and abstracting seasonal cycles from these data and in forecasting by using concepts of fuzzy sets.This Fuzzy Time-Series Model is applied to analyzing the sales volume of department stores and of supermarkets and to forecasting these sales volumes in the following year.
