Statistics is a branch of mathematics in which groups of measurements or observations are studied. The subject is divided into two general categories—
. In descriptive statistics one deals with methods used to collect, organize and analyze numerical facts. Its primary concern is to describe information gathered through observation in an understandable and usable manner. Similarities and patterns among people, things and events in the world around us are emphasized. Inferential statistics takes data collected from relatively small groups of a population and uses inductive reasoning to make generalizations, inferences and predictions about a wider population.
Throughout the study of statistics certain basic terms occur frequently. Some of the more commonly used terms are defined below:
is a complete set of items that is being studied. It includes all members of the set. The set may refer to people, objects or measurements that have a common characteristic. Examples of a population are all high school students, all cats, all scholastic aptitude test scores.
A relatively small group of items selected from a population is a
. If every member of the population has an equal chance of being selected for the sample, it is called a
. Examples of a sample are all algebra students at Central High School, or all Siamese cats.
are numbers or measurements that are collected. Data may include numbers of individuals that make up the census of a city, ages of pupils in a certain class, temperatures in a town during a given period of time, sales made by a company, or test scores made by ninth graders on a standardized test.
are characteristics or attributes that enable us to distinguish one individual from another. They take on different values when different individuals are observed. Some variables are height, weight, age and price. Variables are the opposite of
whose values never change.