Represents the characteristics that are typical for— that is, exhibited by—most members of a particular group.
For statistical purposes, normal means whatever is average for a given group of people ("the norm"). Therefore, the term normal does include those group members who deviate significantly from the measures of central tendency (the mean, the median, or the mode) of a given distribution.
The term normal is fundamentally statistical and quantitative. In testing and measuring, for example, normal can be defined as a central cluster of scores in relation to a larger grouping. In intelligence testing normal is also defined by the average, or mean, which is established as an IQ score of around 100.
However, in many contexts normal is a subjective term that is very difficult to define. In the absence of fixed standards, normal and abnormal are often defined in terms of each other. However, rather than a simple pairing of opposites, they are generally thought of as points on a continuum of social adjustment, with normal people possessing certain positive traits to a greater degree, while abnormal people are characterized by deficiencies in these traits. Some of the traits that help define psychological normalcy are efficient perception of reality; self-knowledge; self-control; ability to form affectionate relationships; self-esteem; and productivity. The notion of defining normalcy in terms of social adjustment has its detractors, who argue that such a definition places too much emphasis on conformity and too little on such traits as individuality and creativity.
Martin, David W. Doing Psychology Experiments. 2nd ed. Monterey, CA: Brooks/Cole, 1985.
Berman, Simeon M. Mathematical Statistics: An Introduction Based on the Normal Distribution. Scranton, PA: Intext Educational Publishers, 1971.