APA style for program used in a study
According to Section 7.08 (page 210) of the 6th edition of the Publication Manual of the APA,


  Do not italicize the names of software, programs, or languages.


Furthermore,


  Reference entries are not necessary for standard software and programming languages, such as Microsoft Word or Excel, Java, Adobe Photoshop, and even SAS and SPSS.  In text, give the proper name of the software, along with the version number.  Do provide reference entries for specialized software or computer programs with limited distribution.


An example of a reference entry:


  Comprehensive Meta-Analysis (Version 2) [Computer software]. Englewood, NJ: Biostat.