Trapezoidal and triangular approximations preserving the expected interval

In this paper, an improvement of the nearest trapezoidal approximation operator preserving the expected interval is studied, which proposed by Grzegorzewski and Mrowka. A formula for computing the improved approximation is presented. Moreover, the nearest triangular approximation operator preserving the expected interval is also investigated. (c) 2007 Elsevier B.V. All rights reserved.