In the 1920’s, two world-renowned social scientists, Dr. Carl Jung and Dr. William Marston,developed the four-quadrant theory of behavior. Each scientist concentrated their work in different specialties. Dr. Jung studied dysfunctional personalities while Dr. Marston focused on the behavior of normal people. Born in Cliftondale, Massachusetts, in 1893, Dr. Marston received his PhD at Harvard University in 1921. In 1928 he published the book, "The Emotions of Normal People," a best-selling classic for many years in which he described the theory we use today. The DISC is based on Dr. Marston’s work and is the ideal tool to accelerate the process of individual growth, identify strengths and weaknesses, and rapidly develop improved communication strategies.
The DISC Report consists of just 24 questions and can graph over 19,000 individual responses, resulting in 384 different behavioral styles. the DISC Instrument accurately distributes them across the remaining 368 graphs. As a result, the DISC Instrument is far more sophisticated than instruments that only measure one factor against another in each question.
DISC is the leading behavioral assessment in the world, experienced by over four million people,and now more widely used than the Myers-Briggs Type Indicator. One of the main reasons for this is that the DISC has been empirically validated at 91%, as high as any assessment in the world based on behavioral styles. In 1984 the DISC was computerized and today provides 40,000 behavioral characteristics.
Extensive research has been conducted on the reliability and validity of the DISC Instrument in the following areas:
Test-Retest Reliability - the stability of test scores over time
Construct Validity – the ability to measure a specific trait
Concurrent Validity – a relationship to other tests measuring similar constructs
Content Validity – the ability to measure what it is supposed to measure
Predictive Validity – the ability to predict performance on another activity
Scores on the DISC Instrument exhibit very little change over time. Six-month test-retest correlations average in the .90 range. The DISC Instrument is a reliable instrument that consistently measures the same thing.
Construct and Concurrent Validity
Significant correlations have been found across all four DISC dimensions. This indicates that the DISC Instrument validly assesses constructs measured by other Four Factor assessment instruments.
The DISC dimensions can differentiate good performances from poor performances in studies of sales performance and managerial ability in a number of industries from truck drivers to Fortune 500 companies. The DISC Instrument successfully distinguishes varying levels of performance.
Outcome measures as diverse as sales performance, turnover rates, and job injuries have been predicted with a high degree of accuracy on the basis of DISC scores making the DISC Instrument a very valuable tool in selection and management.
The DISC Instrument is deceptively simple, asking respondents to choose what they are "most" and "least" like in 24 separate situations. Yet some 19,630 different
graphs can be plotted from the 24 "most" responses; and 19,680 different graphs from the "least" responses. For practical evaluation purposes, these are condensed into one of 384 different graphs yielding a very high validity rate.
The Spearman-Brown “split-halves reliability coefficient” indicates the degree of internal consistency of response to the DISC Instrument as a whole. The coefficients for each dimension are as follows:
Dominance – “D” r = .92
Influence – “I” r = .89
Steadiness – “S” r = .91
Compliance – “C” r = .90
Strength of the correlation is indicated by the size of the coefficient. The coefficient can vary from +1.00 through 0 to –1.00. A coefficient near 0 tells us there is no relationship between the variables. The closer a coefficient is to + or – 1.00, the stronger the relationship. The above reliability coefficients show an unusually high degree of internal consistency in response to the DISC Instrument as a whole and to each of the related dimensions.
+/- 1.00 = Perfect correlation (extremely rare)
+/- .80 - .99 = Unusually high correlation
+/- .70 - .79 = Very high correlation
+/- .60 - .69 = High correlation
+/- .30 - .59 = Moderately high correlation
+/- .20 - .29 = Very low correlation
+/- .00 - .19 = No correlation
Graph I represents the “most like” behavior, displaying the intensity of the four factors which allows interpretation of the behavior an individual believes must be projected to achieve success in a given environment.
Graph II represents the “least like” behavior, demonstrating the real self, or the intensity of each factor, while the individual is under pressure and unable to mask behavior. The “least” graph is very important as it represents the real person, allowing conclusions to be drawn on how to best understand, manage and communicate with this person.
Based on the individual’s responses to the 24 “most” words, 19, 630 different graphs can be plotted and 19,680 different graphs can be plotted for the “least” responses. The magnitude of those numbers makes it impractical to write an evaluation of each potential graph so, for evaluation purposes, these possible graphs are condensed into one of 384 graphs. The computer-generated reports are based on evaluating the 384 graphs from both the “most” and the “least” responses.
Wikipedia, The DISC Assessment
The History of DISC Assessmnet