 Statistics is a mathematical and conceptual discipline that focuses on the relation between data and hypotheses. The data are recordings of observations or events in a scientific study, e.g., a set of measurements of individuals from a population. The data actually obtained are variously called the sample, the sample data, or simply the data, and all possible samples from a study are collected in what is called a sample space. The hypotheses, in turn, are general statements about the target system of the scientific study, e.g., expressing some general fact about all individuals in the population. A statistical hypothesis is a general statement that can be expressed by a probability distribution over sample space, i.e., it determines a probability for each of the possible samples. 