Fuzzy linear regression with spreads unrestricted in sign

Abstract By the use of actual examples, it is shown that when the two trends, namely the fuzzy spread trend and the center line, or modal, trend, are in conflict or inconsistent, the results of the fuzzy linear regression (FLR) model based on the approach of Tanaka and coworkers frequently misinterprets the data. To avoid this misinterpretation, a modification of the FLR procedure, by allowing the spreads of the parameter to be unrestricted in sign, is proposed. It is shown that by the use of this unrestricted fuzzy linear regression (UFLR) model, correct prediction of the trends are obtained.