Answers are grounded in this paper and cite their sources.
This note develops an alternative definition of the “delta scale” of item difficulty that is used at ETS. A comparison is given with the traditional definition of the delta scale that is based on the normal distribution. Some advantages of the alternative scale are mentioned.
No takes yet. Share an insight, caveat, or question.
Holland et al. (1985) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: