Question

​Explain the conceptual and analytical distinctions between classical test theory and item response theory?

Answer 1

• Classical test theory (CTT) and item-response theory (IRT) are testing item assessment approaches.
• CTT's purpose is to recognize and develop the reliability of psychological tests and assessment; which is measured through the performance of the individual taking the test and the difficulty level of the questions/tasks in the test.The basis for CTT rests upon aspects of a total test score made up of multiple items.
• Item response theory (IRT) looks at the relationship between candidate ability and the difficulty of the test they are taking. It does this by studying a number of variables such as design, analysis and scoring of assessments, under the assumption that each question or task in the test is different from the other; making this theory relatively more mathematically sophisticated.
• Item response theory is ,much more flexible in approach than classical test theory.
• CTT which is also known as true score theory, assumes that each person has a true score,  that would be obtained if there were no errors in measurement. A person’s true score is defined as the expected score over an infinite number of independent administrations of the scale. It is assumed that observed score (X) = true score (T) plus some error (E).
• IRT requires several items so that there is adequate opportunity to have a sufficient range for levels of item difficulty and person attribute. Single-item measures, or too few items, are not suitable for IRT analysis.