Abstract: Many-Facet Rasch model (MFRM) of Item Response Theory (IRT) is applied to performance assessment. Domestic and foreign researches applied MFRM in many fields such as analysis of various examinations, medical diagnosis, judgments of life quality and so on. In these assessment tests, ratings were influenced by a variety of factors among which judges played the most important part. This thesis mainly probed into issues covering subjects, judges, rating scales and rating deviation in Leaderless Group Discussion (LGD) of personnel assessment center in personnel assessment to improve the effectiveness and stability of assessment. This study adopted the FACETS software, a MFRM computer statistics program, to establish 3 facets of subjects, judges and rating dimensions to analyze subjects’ abilities, rater severity, inter-rater reliability, dimension difficulty and rating scales. Meanwhile, this study got results of deviation analysis of subjects and judges, judges and dimensions, deviation among judges, subjects and dimensions. The results illustrated significant differences existed among levels of subjects’ ability, rater severity, dimension difficulty and the rating scale. Differences of rater severity generally did not affect the test scores of subjects. Except some judges, other judges’ ratings had good internal consistency. Dimension difficulty could better distinguish subjects’ ability but judges tended to concentrate on using an intermediate rating scale; The results of deviation analysis of judges and subjects, judges and dimension showed that untrained judges E, F had more rating deviations, so it was necessary to monitor their scores and strengthen the training of the two judges. The application of MFRM, IRT’s expansion, to assessment center evaluation could enable evaluators to make the employment decision by estimated ability level of subjects, design tests according to dimension difficulty, set the standards for training and selection referring to examine judges’ ratings rater severity and inter-rater reliability, improve the assessment process based on a variety of deviation analysis, and finally promote scientific, standardized and precise development of evaluation system of assessment center.

Key words: leaderless group discussion, many-facet Rasch model, item response theory, personnel assessment