The purpose of this Guide is to provide both logical and empirical evidence for medical teachers to improve their objective tests by appropriate interpretation of post-examination analysis. This requires a description and explanation of some basic statistical and psychometric concepts derived from both Classical Test Theory (CTT) and Item Response Theory (IRT) such as: descriptive statistics, explanatory and confirmatory factor analysis, Generalisability Theory and Rasch modelling. CTT is concerned with the overall reliability of a test whereas IRT can be used to identify the behaviour of individual test items and how they interact with individual student abilities. We have provided the reader with practical examples clarifying the use of these frameworks in test development and for research purposes.