10 Questions
Which of the following is a difference between Classical Test Theory (CTT) and Item Response Theory (IRT)?
CTT assumes item characteristics are invariant, while IRT assumes they are group-dependent
What is a shortcoming of Classical Test Theory (CTT) that Item Response Theory (IRT) attempts to overcome?
CTT assumes item characteristics are invariant
How do the estimates of item characteristics obtained through IRT methods differ from those obtained through CTT?
They provide a uniform scale of measurement
Which methodology assumes that item characteristics are invariant and provides a uniform scale of measurement?
Item Response Theory (IRT)
What is one way to contrast Classical Test Theory (CTT) and Item Response Theory (IRT)?
By discussing their shortcomings
Which of the following is a key assumption of Item Response Theory (IRT)?
A person's performance on a test item can be predicted by one or more traits or abilities.
What is the purpose of using large samples with known differences in ability or personality traits in IRT methods?
To assess the trait or ability continuum
What is a distinguishing feature of IRT models compared to Classical Test Theory (CTT)?
IRT models provide a uniform scale of measurement, while CTT does not.
What is the primary purpose of evaluating IRT models?
To confirm or reject the predictions made by the models
What is a requirement for the samples used in IRT methods?
The samples must include individuals at different levels in the trait or ability continuum.
Study Notes
Differences between CTT and IRT
- CTT assumes that test scores are a combination of true scores and errors, whereas IRT assumes that test scores are a function of the interaction between person ability and item characteristics.
- IRT attempts to overcome the shortcoming of CTT, which is that it does not account for differences in item difficulties and discrimination.
IRT Methodology
- IRT assumes that item characteristics are invariant, providing a uniform scale of measurement.
- IRT estimates of item characteristics differ from CTT estimates because IRT considers item characteristics in relation to the underlying trait, whereas CTT estimates are based on population parameters.
Key Assumptions and Features of IRT
- A key assumption of IRT is that the probability of a correct response is a function of the person's ability and item characteristics.
- IRT models are distinguishing from CTT in that they are based on a probabilistic framework.
Purpose and Requirements of IRT
- The primary purpose of evaluating IRT models is to assess their fit to the data and to identify potential misfit.
- Large samples with known differences in ability or personality traits are used in IRT methods to provide a range of abilities to estimate item characteristics accurately.
- A requirement for the samples used in IRT methods is that they should be representative of the population of interest.
Test your knowledge on the shortcomings of Classical Test Theory (CTT) with this quiz. Learn about the differences between CTT and Item Response Theory (IRT) and how they impact test development and item analysis.
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