Hi Albert, I'm not sure a question in RG is the best way to get what you are looking for. RG is a place where specific questions can be asked by researchers, and people with too much spare time and a need to be liked will try to answer them.
If you type the question into Google or Youtube you are likely to get what you want.
IRT has many useful applications. Given the open-ended nature of your query, here's a good starting point for learning more about the background and utility of IRT models:
Item Response Theory (IRT) represents a collection of statistical models and methods used in psychological measurements (test theory) mainly for two broad purposes in the measure of health outcomes: item
analysis and scale scoring. For more elaboration and how IRT is applied check this link.Article Advancing Psychometrics in Uganda's Institutions of Higher L...
IRT defines a parametric (logistic) structure with two sets of parameters: one for (testing) items' characteristics and another is for test-takers' performance characteristics (theta-parameters) based on (testing) item responses. Please be noted that, in IRT, theta-parameters is not measure of test-fakers' performance according to Measure Theory while total score in Classical Testing Theory (CTT) is (Total Score is a special case of ability measure, for general ability measure theory, please read Research Total Score and General Total Score
). Therefore, IRT is incorrect theory for high-stake scoring business (Currently, IRT only is applied for low-stake scoring although this is still not theoretically correct). Please see