In most, if not all, studies we collect data to obtain information about an area of research in which we have an interest. For example, we might want to know the level of dental caries in our area. In order to discover this we might need to observe a number of different variables, which could include, age, sex, number of teeth, cavities, fillings, extraction, pain, sepsis and quality of life. This information or data is normally obtained from a sample of the population which can then be summarised, analysed and conclusions drawn. This collection, summarising and analysis of data are what statistics and statistical technique are all about.