Zeng, Lingjia2011-11-032011-11-031995Zeng, Lingjia. (1995). The optimal degree of smoothing in equipercentile equating with postsmoothing. Applied Psychological Measurement, 19, 177-190. doi:10.1177/014662169501900205doi::10.1177/014662169501900205https://hdl.handle.net/11299/117480The effects of different degrees of smoothing on the results of equipercentile equating in the random groups design using a postsmoothing method based on cubic splines were investigated. A computer-based procedure was introduced for selecting a desirable degree of smoothing. The procedure was based on two criteria: (1) that the equating function is reasonably smooth, as evaluated by the second derivatives of the cubic spline functions, and (2) that the equated score distributions are close to that of the old form. The equating functions obtained from smoothing the equipercentile equivalents by a fixed smoothing degree and a degree selected by the computer-based procedure were evaluated in computer simulations for four tests. The results suggest that no particular fixed degree of smoothing always led to an optimal degree of smoothing. The degrees of smoothing selected by the computer-based procedure were better than the best fixed degrees of smoothing for two of the four tests studied; for one of the other two tests, the degrees selected by the computer procedure performed better or nearly as well as the best fixed degrees. Index terms: computer simulation, cubic spline, equating, equipercentile equating, smoothing.enArticle