Behavior Research Methods

, Volume 38, Issue 2, pp 344-352

First online:

An SPSS implementation of the nonrecursive outlier deletion procedure with shiftingz score criterion (Van Selst & Jolicoeur, 1994)

  • Glenn L. ThompsonAffiliated withSchool of Psychology, University of Ottawa Email author 


Sophisticated univariate outlier screening procedures are not yet available in widely used statistical packages such as SPSS. However, SPSS can accept user-supplied programs for executing these procedures. Failing this, researchers tend to rely on simplistic alternatives that can distort data because they do not adjust to cell-specific characteristics. Despite their popularity, these simple procedures may be especially ill suited for some applications (e.g., data from reaction time experiments). A user friendly SPSS Production Facility implementation of the shifting z score criterion procedure (Van Selst & Jolicoeur, 1994) is presented in an attempt to make it easier to use. In addition to outlier screening, optional syntax modules can be added that will perform tedious database management tasks (e.g., restructuring or computing means).