Item response theory requires logically unjustifiable assumptions

• Published in: Quality & quantity 2017-07, Vol.51 (4), p.1549-1561
• Main Author: Krause, Merton S.
• Format: Article
• Language: English
• Subjects: Attributes; Item response theory; Measures; Methodology of the Social Sciences; Operations research; Ordinal measurement; Quantitative psychology; Social Sciences
• ISSN: 0033-5177; 1573-7845
• DOI: 10.1007/s11135-016-0351-0

If items have different levels of difficulty (or sensitivity) relative to some psychological attribute, passing (or endorsing) any one cannot mean the same about a person as passing any other, so percent of items passed regardless of which these are cannot indicate a person’s level on any attribute. If persons have different levels on a psychological attribute, an item’s being passed by one person cannot mean the same about its difficulty level as being passed by any other person, so percent of persons passing it regardless of which persons these are cannot indicate the item’s difficulty level. Percent of items passed by a person and percent of persons passing an item are incommensurate quantities not expressible in terms of the same quality or dimension. Both such percents are dependent on what sample of items and of persons are used. A person’s attribute level is not demonstrably probabilistic, because truly independent replicate occasions of a person responding to an item are impossible. Passing an item depends on more than a person’s single attribute level, the item’s difficulty level, and random chance. On all these matters Item Response Theory relies on assumptions that are logically unjustifiable.