Based on a short interval (5-week) test-retest reliability of 0.82 and a standard deviation for the E1 scale of 25
(Howes & Carskadon, 1979), The standard error of measurement is approximately 10.6 = 25 V 1.82Z points. This
means that raw scores with a 21-point difference are considered statistically significant.
The publishers do a very good job of promoting the test and providing support for its users. The MBTI also has much intuitive appeal. The descriptions of each type are generally flattering and sufficiently vague so that most people will accept the statements as true of themselves. If you tell people that they are "innovative thinkers and good problem solvers, and good at understanding and motivating people, but may have trouble following through on
details of a project," they will believe that the statement is an accurate description of themselves regardless of thetruth of the statement. This phenomenon is known as the "Barnum Effect," named in honor of the great entertainer.