The concept of Computer Adaptive Testing (CAT) is a revolutionary approach to assessment that customizes the test experience in real-time to match the individual ability level of the test taker.

Here are the core components and concepts:
1. Tailored Assessment
* The Basic Idea: Unlike traditional fixed-form tests where everyone answers the same set of questions, CAT uses a computer algorithm to select and administer test items (questions) that are individually matched to the test-taker's current estimated ability. It's often called "tailored testing."
* How it Works: The test usually begins with an item of moderate difficulty.
* If the test-taker answers correctly, the next item selected will be more difficult.
* If the test-taker answers incorrectly, the next item selected will be easier.
* This continuous process of evaluation and item selection allows the test to quickly converge on the examinee's true ability level.

2. Efficiency and Precision
* Fewer Items: By constantly adjusting difficulty, CAT avoids wasting the test-taker's time on questions that are either trivially easy or frustratingly difficult. This allows it to achieve the same or higher level of measurement precision with significantly fewer items (sometimes 50% fewer) than a traditional test.
* Time Saving: Fewer items translate directly to a shorter test duration.
* Increased Precision: The items administered are the most informative—those that are a good match for the test-taker's estimated ability—leading to a more accurate and reliable score.
3. Key Technical Foundations

* Item Bank: A large pool of pre-calibrated test questions, each with established difficulty and discrimination parameters.
* Item Response Theory (IRT): The statistical framework essential for CAT. IRT allows the algorithm to:
* Estimate the test-taker's ability level after each response.
* Select the most optimal item from the bank (the one that provides the maximum information for the current ability estimate) to administer next. The ideal item is often one the test-taker is estimated to have a 50% chance of answering correctly.
* Termination Criteria: The algorithm continues adapting until a pre-determined condition is met, such as:
* A minimum number of items have been administered.
* The estimate of the test-taker's ability has reached a high level of precision (i.e., the standard error of measurement is sufficiently small).

4. Benefits
* Motivation: The test-taker is consistently challenged at an appropriate level, which can make the experience more engaging and less frustrating.
* Security: Because each test-taker receives a different set of items, the chances of item exposure and cheating are dramatically reduced.
* Personalization: The assessment experience is entirely individualized, providing a unique measure of each person's standing on the ability scale.
* Immediate Results: Scoring can often be computed instantly upon test completion.

CAT is an adaptive, data-driven assessment method that uses an algorithm and an item bank, grounded in Item Response Theory, to personalize the difficulty of the test in real-time. Its primary goal is to maximize the accuracy of the ability estimate while minimizing the number of questions administered.