FREE BIG FIVE PERSONALITY TEST
The Big Five was originally derived in the 1970's by two independent research teams -- Paul Costa and Robert McCrae (at the National Institutes of Health), and Warren Norman (at the University of Michigan)/Lewis Goldberg (at the University of Oregon) -- who took slightly different routes at arriving at the same results: most human personality traits can be boiled down to five broad dimensions of personality, regardless of language or culture.
These five dimensions were derived by asking thousands of people hundreds of questions and then analyzing the data with a statistical procedure known as factor analysis. It is important to realize that the researchers did not set out to find five dimensions, but that five dimensions emerged from their analyses of the data. In scientific circles, the Big Five is now the most widely accepted and used model of personality (though of course many other systems are used in pop psychology and work contexts; e.g., the MBTI).