Each member of a sample was seen in intensive 1-3 day assessments at the Institute. The assessments were based on the theories and methods described by Heny Murray in his classic book Explorations in Personality (1938) and also in his book on the wartime work of the Office of Strategic Services titled Assessment of Men (1948).
Typically, 15-18 observers studied the assessees at the Institute in groups of 10. The assessees were interviewed 2-3 times, were asked to take a wide assortment of cognitive, interest, and personality tests, and were observed by staff in a variety of situations such as leaderless group discussions, roleplays, and meals.
On the basis of these observations, but without knowledge of any of the test scores, staff members independently assigned trait ratings, Q-sort formulations, and adjectival descriptions to each individual.
... Altogether 62 women and 127 men were included in the assessment staff.... From informal records, we estimate that the modal MBTI type was INFP. Most staff took part in 1-2 assessments, although a few participated in 9+.
Twelve different assessment programs took place between 1957 and 1984.