Statistical theory is a branch of mathematics that deals with the collection, analysis, interpretation, and presentation of data. It provides the framework for making inferences about populations based on sample data, using concepts such as probability, distributions, and hypothesis testing. This theory is essential in various fields, including economics, psychology, and medicine, as it helps researchers draw conclusions and make predictions. By applying statistical methods, scientists can assess the reliability of their findings and determine the significance of their results, ultimately guiding decision-making processes.