Dexter is an R package for managing and analyzing data from educational tests and other projects involving individual assessment.
Dexter caters for the needs of researchers and practitioners in summative assessment (high stakes exams) and educational surveys where the goal is to take a snapshot of a person or a population. It is not specifically intended for formative assessment where new, computer-based learning environments call for dynamic tracking of ability.
Packages differ in scope and purpose. Dexter is targeted at practical testing. This is evident in the strong emphasis on data management and in the attention given to ‘details’ whose relevance only becomes apparent in practice.
Testing, especially high stake exams, involves both a measurement side, preoccupied with validity and reliability, and a contest side where the focus is on being fair and understandable. Dexter tries very hard to achieve the necessary balance between the two goals. All models have sufficient statistics, fit statistics and graphs are based on observable quantities, scoring rules are transparent. There are no attempts to improve fit with models that are nearly or actually unidentifiable.
Dexter covers most needs for practical analysis of summative tests in R. Three other related packages offer extensions for special circumstances.
Dexter can be installed from CRAN in the normal way. The dexter fundamentals vignette gives an accessible yet comprehensive introduction to dexter.