Statistics can be further subdivided into two broad categories, applied and theoretical, that focus on different aspects of this particular discipline. In descriptive statistics, for example, methods are used to summarize or describe a set of data. Inferential statistics studies patterns in the data which may be modeled in a way that accounts for randomness and uncertainty in observations. These models are then used to draw inferences about the process or population under study. Together descriptive and inferential statistics comprise a subfield of statistics called applied statistics. Mathematical statistics, on the other hand, is concerned with studying the rigorous theoretical aspects of the subject.