For two-way contingency tables with ordered categories, Yamamoto et al. (2011) and Yamamoto et al. (2012b) considered proportional reduction in error (PRE) measures, which describe the relative decrease in the probability of making an error in predicting the value of one variable when the value of the other variable is known, as opposed to when it is not known. The present paper proposes a new PRE measure for the symmetric situation in which explanatory and response variables are not defined clearly for two-way contingency tables with ordered categories. The measure proposed includes measures of forms of harmonic, geometric and arithmetic means. An example is also given.