Minichan

The MBTI is "one of the most popular personality questionnaires".[52] Some researchers have interpreted the reliability of the test as being low. Studies have found that between 39% and 76% of those tested fall into different types upon retesting some weeks or years later.[38][41]

One study reports that the MBTI dichotomies exhibit good split-half reliability; however, the dichotomy scores are distributed in a bell curve, and the overall type allocations are less reliable. Also, test-retest reliability is sensitive to the time between tests. Within each dichotomy scale, as measured on Form G, about 83% of categorizations remain the same when individuals are retested within nine months, and around 75% when individuals are retested after nine months. About 50% of people tested within nine months remain the same overall type, and 36% remain the same type after more than nine months.[53] For Form M (the most current form of the MBTI instrument), the MBTI Manual reports that these scores are higher (p. 163, Table 8.6).

In one study, when people were asked to compare their preferred type to that assigned by the MBTI assessment, only half of people picked the same profile.[54] Critics also argue that the MBTI lacks falsifiability, which can cause confirmation bias in the interpretation of results.

A number of scholars argue that criticisms regarding the MBTI mostly come down to questions regarding the validity of its origins, not questions regarding the validity of the MBTI's usefulness.[55] Others argue that the MBTI can be a reliable measurement of personality; it just so happens that "like all measures, the MBTI yields scores that are dependent on sample characteristics and testing conditions".

In her research, Isabel Myers found that the proportion of different personality types varied by choice of career or course of study.[1]:40–51[9] However, some researchers examining the proportions of each type within varying professions report that the proportion of MBTI types within each occupation is close to that within a random sample of the population.[38] Some researchers have expressed reservations about the relevance of type to job satisfaction, as well as concerns about the potential misuse of the instrument in labeling individuals.[38][57]

CPP became the exclusive publisher of the Myers-Briggs instrument in 1975. They call it "the world's most widely used personality assessment", with as many as two million assessments administered annually.[58] CPP and other proponents state that the indicator meets or exceeds the reliability of other psychological instruments and cite reports of individual behavior.[59][60][61]

Some studies have found strong support for construct validity, internal consistency, and test-retest reliability, although variation was observed.[62][63] However, some academic psychologists have criticized the MBTI instrument, claiming that it "lacks convincing validity data",[33][40][41][64] while some studies have shown the statistical validity and reliability to be low.[38][41][65]

Studies suggest that the MBTI is not a useful predictor of job performance.[38][43][66] As noted above under Precepts and ethics, the MBTI measures preference, not ability. The use of the MBTI as a predictor of job success is expressly discouraged in the Manual.[7]:78 However, the MBTI continues to be popular because many people are qualified to administer it, it is not difficult to understand, and there are many supporting books, websites and other useful sources which are readily available to the general public.[67]