SPSS and SAS programming for the testing of mediation models.

BACKGROUND Mediation modeling can explain the nature of the relation among three or more variables. In addition, it can be used to show how a variable mediates the relation between levels of intervention and outcome. The Sobel test, developed in 1990, provides a statistical method for determining the influence of a mediator on an intervention or outcome. Although interactive Web-based and stand-alone methods exist for computing the Sobel test, SPSS and SAS programs that automatically run the required regression analyses and computations increase the accessibility of mediation modeling to nursing researchers. OBJECTIVES To illustrate the utility of the Sobel test and to make this programming available to the Nursing Research audience in both SAS and SPSS. METHODS The history, logic, and technical aspects of mediation testing are introduced. The syntax files sobel.sps and sobel.sas, created to automate the computation of the regression analysis and test statistic, are available from the corresponding author. RESULTS The reported programming allows the user to complete mediation testing with the user's own data in a single-step fashion. A technical manual included with the programming provides instruction on program use and interpretation of the output. CONCLUSION Mediation modeling is a useful tool for describing the relation between three or more variables. Programming and manuals for using this model are made available.