Determine the distance between points P(O, 0, 0, 0) and M ( 1, 0, 0, 1) in Minkowski geometry. This reveals another interesting aspect of this geometry, namely that noncoincident points can be zero distance apart. The special theory of relativity gives a physical interpretation to such a line PM, all of whose points are zero distance apart; it is the path of a photon, a light particle.

Statistics is the science of collecting, classifying, presenting and interpreting data. Where Does Data Come From • Individuals o The objects described by a set of data. The objects can be people, animals or things. • Variable o Any characteristic of an individual. Variables can take different values for different individuals. Data Sources • Observational Study o Observes individuals and measures variables of interest but does not attempt to influence the responses. o The purpose of an observational study is to describe some group/situation. • Sample Survey o A sample survey is a type of observational study in which a sample is selected