The Applied Study On Genetic Algorithm In Parameter Estimation Of Two Parameters Logistic Model On Item Response Theory

Having thoroughly studied the item response theory, the two parameters logistic model, this article proposes a kind of parameter estimation method based on the genetic algorithm and the two parameters logistic model methods, and also works out a relevant arithmetic program to estimate the different item parameters.Item response theory is one of the modern educational and psychological measure theories. Parameter estimation is the premise of utilizing the item response theory, it is necessary to estimate these parameters out for the application of establishing question base, evaluating the subject and evaluating the quality of examination, etc. It can be said that the developing history of item response theory is the developing history of capability parameter and item parameters.Recent parameter estimation methods are mainly the maximum likelihood method and Bayer's method, the important parts of these methods are to obtain the likelihood function, select the initial value of the parameter estimation and the derivative on unknown parameters. However, if the initial value is not proper, the real value could not be convergence, and even surge, this is not the phenomenon the administrator expected. In the meanwhile, the calculation of both parameter seeking differential coefficient and second order partial derivative are very difficult process. Each iteration must bring some errors, with the increase of the iterative times,errors would be larger, therefore , this article put forward a new kind of parameter estimation methods according to those disadvantages mentioned above. That is to say, to estimate the parameter by the thinking of genetic algorithm, this method is not strict in the parameter initial value, and it doesn't necessarily need any data of unevaluated parameter.Genetic algorithm is a premium seeking method,with the characters of self-adaptation, whole optimization, and concealed parallel processing .The author proposes the improving strategies of genetic operators and the speedup constringency strategies and work out the arithmetic validating program through the analysis and research of coding and genetic operators on genetic algorithm. Compared with the popular foreign software BILOG, and to some extent, the estimation method just mentioned can make a better constricted answer.