How Reliable Is The DISC Personality Test


With technology at the centre of any business, reliability is a significant factor in buying decisions. We want our laptops and other essential equipment to stand the test of time. As with any other technology, we also need our DISC assessments to be reliable and consistently and accurately identify employees DISC personality type. So, what does reliability mean in terms of the DISC Personality Test? And how reliable is the DISC Personality Test?

Reliability of DISC Assessment Profiles

When we call something reliable, we are referring to its dependability and consistency. It’s no different in statistics and psychometrics. In psychometrics, reliability refers to the consistency of a measure, which means that it produces a similar or the same result under consistent conditions. Why is consistency important in a DISC Personality Test? Well, when you measure a person’s DISC Personality with an instrument twice, you want it to produce the same result (or very close to it) both times. This form of reliability testing is called test-retest reliability, and it is an essential measure of any psychometric or DISC personality testing instrument.

Reliability of DISC assessment profiles refers to their consistency of results. It ensures the DISC assessment profile produces the same or similar results every time a candidate completes the questionnaire. One of the most common measures of reliability is test-retest reliability. Using this method, researchers evaluate the test by administering an assessment twice at two different points in time. This type of reliability assumes that there will be no change in the measure of the behaviour. When a DISC assessment tool provides a person with the same DISC style at two different points in time, we can presume it has test-retest reliability.

Internal consistency is another technique organisations use to measure the reliability of DISC assessment profiles. Internal consistency measures whether several items that suggest they measure the same general construct produce similar scores. Cronbach’s Alpha, a statistic calculated from the correlation between items, is typically used to measure Internal Consistency. Internal consistency scores range from zero to one. The commonly-accepted rule of thumb is that an alpha of 0.6-0.7 indicates acceptable reliability and 0.8 or higher indicates good reliability. Reliability scores of 0.95 and higher are not necessarily desirable, indicating that the items may be entirely redundant. 

Another measure to evaluate DISC assessment profiles’ reliability is the presence of an adjusted and natural profile. We expect to observe some variance in psychometric test results due to different conditions, i.e. current work environment and other extenuating circumstances. Two profiles contribute to DISC assessment profiles’ reliability by accounting for individuals adjusted and natural behaviours. Some DISC personality testing instruments only report on an individual’s adjusted type leading to a significant variance in results upon retesting. Extended DISC® Assessments, one of the most reliable DISC personality tests, contain two profiles. Profile I reports on a person’s current or adjusted style. We expect this to change based on their current environment. Whereas Profile II identifies the person’s natural or unconscious Extended DISC® style, we expect this to be more stable over a person’s lifetime. 

Unfortunately, most psychometric assessment tools and DISC personality tests do not meet the industry standards for the validation criterion. Some DISC assessment profiles use only one technique to measure their instrument’s reliability and claim their product is dependable. Furthermore, they base their reports on a person’s adjusted style, leaving the profile vulnerable to considerable variance in DISC type. As a result, researchers and psychology professionals often call the reliability of DISC assessment profiles into question.

Although the vast majority of DISC assessments’ reliability is questionable, the most reputable DISC personality tools consistently receive strong reliability scores. Extended DISC® assessments are among the most reliable, valid, and accurate DISC personality tools on the market. Scientifically backed through ReliaDATA our validation and reliability measures, Extended DISC® continually achieves the highest score across several validation and reliability measures.

Most Reliable Personality Test

An overwhelming amount of psychometric and DISC personality tests lack the studies and reports to verify their accuracy and reliability. Several instruments that do have validation reports available do not meet industry standards for validation and reliability. 

We believe that organisations should have the most reliable personality tests and accurate data to make confident people-based decisions. Extended DISC® assessments are among the most reliable personality tests available. Our personality tests are scientifically-backed by ReliaDATA, our comprehensive bi-annual validation study. ReliaDATA is the industry-leading validation study demonstrating trends, reliability, and validity of Extended DISC® psychometric reports generated worldwide. ReliaDATA ensures that our clients confidently use the most accurate and reliable DISC assessments available on the market. Our DISC assessment tools’ validity lends itself to organisations’ credibility, ensuring they use authentic and scientifically backed tools to make personnel decisions. 

Extended DISC® Assessments have another in-built reliability mechanism, where the online system will flag a result as invalid if a respondent does not establish a clear answering pattern. Some DISC tools never provide an invalid report. Therefore, a candidate can randomly select an answer or try to ‘cheat’ the system, and the instrument will still produce a result. One of Extended DISC®’s strengths is that it will not generate a report if it cannot accurately identify a DISC style. Only 2.93% of all results are deemed invalid in Australia. Globally the overall figure is 4.13%. 

Myers Briggs Validity and Reliability

Myers Briggs has been around for some 60 plus years. It is a well-known and well-respected system. Although one of the most widely known personality tests available, Myers Briggs validity and reliability regularly receives criticism. One of the most frequent complaints the Myers Briggs gets is related to its low test-retest reliability. A person who takes the Myers Briggs assessment on two separate occasions is relatively likely to receive different results from one instance to another. Myers Briggs determines personality in dichotomies, an either-or choice that separates people clearly into one of two groups. For example, in Myers Briggs, a person is either an Introvert or Extrovert. Most of the test-retest variability surrounds the dichotomous nature of the assessment. People who fall close to the average can easily move to the opposite side of the dichotomy when retested. Although the Myers Briggs Foundation website boasts that 75% – 90% of people have three to four traits the same on a retest, research suggests this could be as low as 50%.

MBTI Reliability and Validity

It’s important to note that even though a tool is reliable, it may not be valid. To determine the reliability of a tool, researchers evaluate if an instrument measures in a way that is consistent and dependable. If the results from a tool contain a lot of random variation, it will be deemed less reliable. The second aspect they evaluate is validity and whether an instrument measures accurately. Validity is the degree to which an assessment tool measures what it intends to measure.

One of the first institutions interested in MBTI was Educational Testing Services, ETS (otherwise known as the organisation who create the SAT’s). They were interested in finding a personality test to help universities determine their admissions. They tried to validate MBTI, but their team of statisticians could not find proof that the questionnaire measured the categories that it claimed to measure, or that it was even reliable. Over 50% of people who took it got a different result when they took it a second time.

MBTI reliability and validity is often called into question for its lack of validity, meaning it does not predict what it says it will predict. Researchers often call out MBTI on its ability to accurately link the “types” to outcomes in the real world. For example, how well people of a specific type will perform in a given role. Often used for career guidance and planning, there is a lack of research that supports the idea that MBTI can predict positions in which a person will succeed.

Despite overall lack of validity and reliability, MBTI has become a global language in which you can say a lot about yourself just by introducing your type. The language of the type and introducing yourself by saying things like, “I’m an ENTJ” has become so prevalent and meaningful, regardless of its scientific accuracy.

DISC assessments are powerful tools to use in team building, leadership development, and recruitment. When selecting which DISC assessment to use, it’s essential to ask questions regarding the assessment’s reliability and validity. These questions should form a significant part of your decision to ensure you are confident in your selected tool.