The MBTI instrument

The MBTI preferences indicate the differences in people based on the following:^[4]

• How they focus their attention or get their energy (extraversion or introversion)
• How they perceive or take in information (sensing or intuition)
• How they prefer to make decisions (thinking or feeling)
• How they orient themselves to the external world (judgment or perception)

By using their preference in each of these areas, people develop what Jung and Myers called psychological type. This underlying personality pattern results from the dynamic interaction of their four preferences, in conjunction with environmental influences and their own individual tendencies. People are likely to develop behaviors, skills, and attitudes based on their particular type. Each personality type has its own potential strengths as well as areas that offer opportunities for growth.
The MBTI tool consists of multiple choice questions that sort respondents on the basis of the four "dichotomies" (pairs of psychological opposites). Sixteen different outcomes are possible, each identified by its own four-letter code, referred to by initial letters. (N is used for iNtuition, since I is used for Introversion). The MBTI is approximately 75% accurate according to its own manual.^[5]

• I – Introversion preferred to extraversion: ISTJs tend to be quiet and reserved. They generally prefer interacting with a few close friends rather than a wide circle of acquaintances, and they expend energy in social situations (whereas extraverts gain energy).^[6]
• S – Sensing preferred to intuition: ISTJs tend to be more concrete than abstract. They focus their attention on the details rather than the big picture, and on immediate realities rather than future possibilities.^[7]
• T – Thinking preferred to feeling: ISTJs tend to value objective criteria above personal preference. When making decisions, they generally give more weight to logic than to social considerations.^[8]
• J – Judgment preferred to perception: ISTJs tend to plan their activities and make decisions early. They derive a sense of control through predictability. ^[9]