Raw Scores Are Not Linear Measures: : Rasch vs. Classical Test Theory CTT Comparison | ||
---|---|---|
Standing | Raw Scores | Linear Measures |
Psychometrics | Classical Test Theory CTT | Rasch Model RM |
Data | must be "complete" | robust against missing data and non-administered items |
Meaning | ordinal ranking on hoped-for latent variable | linear positioning on latent variable explicitly-defined by item content |
Status | mistaken for truth | known as estimates |
Additivity | non-linear, bent | linear, straight |
Continuity | discrete, lumpy | continuous, smooth |
Precision | unknown, except on average | quantified by standard errors |
Accuracy | unknown | quantified by local fit statistics |
Linear Analysis | unsuited to usual statistics | ideal for usual statistics |
Validity | sample-dependent test "reliability" | item-dependent construct validity |
Diagnosis | sample-dependent item point-biserial | individual item and person fit statistics |
Conceptualization | concrete | abstract |
Occurrence | accidental | deliberate |
Construction | irreproducible | reproducible |
Scope | local | general |
Relationships | incomparable | comparable |
Context | test-bound | test-free |
Integration | awkward to equate | simple to equate |
Benjamin D. Wright |
Raw Scores Are Not Linear Measures: : Rasch vs. Classical Test Theory CTT Comparison. B.D. Wright Rasch Measurement Transactions, 1992, 6:1, 208
Forum | Rasch Measurement Forum to discuss any Rasch-related topic |
Go to Top of Page
Go to index of all Rasch Measurement Transactions
AERA members: Join the Rasch Measurement SIG and receive the printed version of RMT
Some back issues of RMT are available as bound volumes
Subscribe to Journal of Applied Measurement
Go to Institute for Objective Measurement Home Page. The Rasch Measurement SIG (AERA) thanks the Institute for Objective Measurement for inviting the publication of Rasch Measurement Transactions on the Institute's website, www.rasch.org.
Coming Rasch-related Events | |
---|---|
Oct. 4 - Nov. 8, 2024, Fri.-Fri. | On-line workshop: Rasch Measurement - Core Topics (E. Smith, Winsteps), www.statistics.com |
Jan. 17 - Feb. 21, 2025, Fri.-Fri. | On-line workshop: Rasch Measurement - Core Topics (E. Smith, Winsteps), www.statistics.com |
May 16 - June 20, 2025, Fri.-Fri. | On-line workshop: Rasch Measurement - Core Topics (E. Smith, Winsteps), www.statistics.com |
June 20 - July 18, 2025, Fri.-Fri. | On-line workshop: Rasch Measurement - Further Topics (E. Smith, Facets), www.statistics.com |
Oct. 3 - Nov. 7, 2025, Fri.-Fri. | On-line workshop: Rasch Measurement - Core Topics (E. Smith, Winsteps), www.statistics.com |
The URL of this page is www.rasch.org/rmt/rmt61n.htm
Website: www.rasch.org/rmt/contents.htm