Item response theory

In this talk, you will learn about Item Response Theory (IRT) and how it compares with Classical Test Theory, particularly in the context of ability and aptitude testing. You’ll explore why IRT places importance on each individual test item and the difficulty of those items, leading to adaptive testing where each candidate may receive a unique set of questions. Key benefits and challenges of IRT are also discussed, including test security, efficiency, and the reasons it takes longer to develop these tests.

After this talk, you will:

• Understand the difference between Classical Test Theory and Item Response Theory (IRT).

• Know why IRT is gaining interest in psychometric testing, especially for ability and aptitude tests.

• Be aware that classical tests give everyone the same items, while IRT adapts questions based on the test taker’s responses.

• Recognise that IRT uses item banks with questions of varying difficulty, making tests more secure and efficient.

• Understand how adaptive testing works—questions change in difficulty depending on the candidate's performance.

• Know the advantages of IRT, such as greater test security and efficiency in estimating ability levels.

• Understand that developing IRT-based tests takes longer and is more complex than classical test theory tests.

• Be familiar with terms like "latent trait theory" and "adaptive testing" as they relate to IRT.

• Appreciate that IRT could represent the future of psychometric testing as more publishers adopt it.

• Know that IRT estimates ability by focusing on the difficulty and discrimination of each test item rather than simply adding up correct answers.