SPSS (currently officially “IBM® SPSS® Statistics”) is a commercially distributed software suite for data management and statistical analysis and the name of the company originally developing and distributing the program. Introduced in 1968, it helped revolutionize research practices in the social sciences, enabling researchers to conduct complex statistical analyses on their own. Presently, Windows, Mac, and Linux versions of SPSS are available with major version updates released every one to two years. SPSS is a comparably easy‐to‐handle statistics program providing commonly used procedures. As such, it is widely used in academia, including in communication studies, although it is facing increasingly tough competition from more comprehensive and free open‐source software.

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Test theory is concerned with methods and criteria for the construction, evaluation and comparison of “tests,” that is, procedures for measuring observables or constructs of interest. These methods and criteria rest on assumptions about the composition of measurements as well as the properties of these components and the relationship among them. The most prominent test‐theoretical frameworks are classical test theory (CTT) and item response theory (IRT), including the Rasch model. Within the CTT framework influential quality criteria like objectivity, reliability, and validity as well as methods for assessing them have been developed. Considering the small number of simple assumptions made by CTT, it has proven quite fruitful, even in comparison to “modern” test theories (e.g., IRT) which overcome certain limitations of CTT at the expense of stronger assumptions and greater mathematical complexity.