OPLM: One Parameter Logistic Model. Computer program and manual. OPLM is also the name of a computer program. OPLM is an MS-DOSWindows application for analyzing item responses within the framework of the One Parameter Logistic Model (OPLM). It can handle items that are scored dichotomously or polychotomously. Because the OPLM model is a generalization of the Rasch model, the program can also perform Rasch analyses and Partial Credit model analyses.