Developing valid measures of abstract constructs is essential to the advancement of psychological and educational research. The most common practice in scale development consists of an administering a group of items intended to measure the same construct and subsequently aggregating the responses to form total a scale value. Besides, reliability of scores, number of underlying constructs, and scale construction practices should empirically test the assumptions of equal item weighting and the linear treatment of scales can represent the quantity of a trait held by an individual. Based on the perspective of using Rasch Model as a model in one sense in that it represents the structure which data should exhibit in order to obtain measurements from the data; i.e. it provides a criterion for successful measurement. As such, measuring the lecturers' beliefs needs a measurable instrument to be developed and tested in order to clarify how beliefs reform lecturers' teaching functions and practices. This book is mainly on how to use Rasch Model analysis as a powerful tool for evaluating constructs validity of the instrument for interpretation the lecturers' beliefs on teaching functions.