Sample interview questions: Can you explain the concept of item difficulty and how it is measured in psychometric assessments?
Sample answer:
Item difficulty is a fundamental concept in psychometric assessments, referring to the level of difficulty associated with a particular item or question. It is a measure of how challenging an item is for the examinees to answer correctly.
Item difficulty is commonly measured using two main methods:
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Classical Test Theory (CTT): In CTT, item difficulty is typically estimated based on the proportion of examinees who answer the item correctly. An item is considered difficult if a small proportion of examinees answer it correctly, and easy if a large proportion answers it correctly. Item difficulty is often expressed as a difficulty index (p-value), which ranges from 0 to 1, with 0 indicating a very difficult item and 1 indicating a very easy item.
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Item Response Theory (IRT): IRT provides a more sophisticated approach to measuring item difficulty. It uses a mathematical model to estimate the difficulty of an item based on the performance of examinees with varying levels of ability. In IRT, item difficulty is typically represented by a parameter called “b-value” or “item discrimination parameter.” A higher b-value indicates a more difficult item, while a lower b-value indicates an easier item.
The measurement of item difficulty is crucial for several reasons:
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Test Fairness: Ensuring that a test is fair and unbiased requires items of varying difficulty levels. A test composed entirely of difficult or easy items may not accurately assess the abilities of examinees across the spectrum of competence.
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Reliability and Validity: Item difficulty is a factor that influences the reliability and validity of a test. A test with a good mix of difficult and easy items is more likely to be reliable and valid than a test with items of uniform difficulty.
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Adaptive Testing: Item difficulty plays a vital role in adap… Read full answer