Learning is the focus of attention for any educational enterprise. Consequently, the quality of assessment of the extent to which learning has occurred is of crucial importance. Assessment plays an important role in education in Hong Kong as in other places. Nevertheless, how to design an assessment that is of high quality, or how to fully utilize the results of the assessment to understand more deeply about the ability of our students is a demanding task for most teachers. It is not uncommon for teachers to assume that those students who cannot get good assessment results are weak students or that they have learning problems. Teachers rarely question the quality of assessment items to be the source of problems. In other words, teachers seldom consider the possibilities that the items may be too difficult, or unsuitable for the students' levels. In fact, it is worth investigating both the students' and items' performances for the assessments in order to understand more about the ability of our students. Under such circumstances, Rasch Measurement Model is a tool that teachers may consider to assist them for interpreting and analyzing the alignment between student ability and assessment item difficulty. In Rasch modelling, the data are checked, using a set of procedures and criteria, for the extent to which they match with the theoretical model. In particular, the point-measure correlations, and the INFIT and OUTFIT statistics are used to assess the goodness of fit between model and data. This study aims to illustrate how teachers can make use of these statistics from Rasch modelling to support them in the implementation of learning oriented assessment. The study will be based on assessment data obtained from two classes of Primary Three Students in a local school in July 2006. In the study, we will focus on the implication of misfit persons and items by using Rasch Measurement Model so as to discuss ways for understanding our students and improving the items and setting

Hong Kong Teachers understand students' abilities and ranked students' position by the scores of quizzes, tests and examination. Setting items for assessing students is therefore one of significant tasks for Hong Kong teachers. Teachers usually set items to access their students based on what they taught in the classroom. Teachers do not usually consider whether the items are set appropriately to measure their students' abilities. On the other hand, it is important for the teachers learn the quality control of item settings. Rasch measurement is a quality control mechanism and good for diagnosis. The area of diagnosis includes item misfit between items and persons, and probability of a person's correctly answering the item against his ability. The diagnostic information obtained can be used by teachers to enhance their assessment tools such that teachers are better informed about their students' learning. Nonetheless, such diagnoses are under-utilised. The aim of this study is to illustrate how the diagnostic information can be generated from Rasch measurement using the Winsteps software, and how teachers can make use of such information to enhance assessment tools. In particular, this study focused on how to use one of the Item Characteristic Curve as a diagnostic tool in order to analyze the relationship between students' abilities and item difficulties. Based on this analysis, teachers can discern the quality of items in the assessment and hence obtain more accurate estimates of students' abilities and item difficulties. The sample for the study involved about 150 Primary Three students from a local school. Students' basic competencies in mathematics at end of Key-Stage-l were gauged in June 2006 using an assessment tool designed by the authors. Rasch measurements of the students were obtained using the Winsteps software. Item Characteristic Curves of the items were analysed to diagnose the psychometric qualities of the assessment tool. Implications for teachers in