"Although various books publish popular tests consisting of 50-70 questions, such as Keirsey Temperament Sorter, these in fact are not valid psychological instruments. Real psychological testing methodologies must include means of verification of correctness of their results, which is impossible to achieve with only several tens of questions.
On the other hand, the Myers Briggs Type Indicator, or Gray-Wheelwright Test, although being valid psychological instruments, detect types DIFFERENT FROM THE SOCIONIC TYPES. The MBTI is a similar but not identical system of types. This means that correlation between Socionics, on the one hand, and MBTI, on the other, is only approximate. For example, if you detected your type as ESFP according to MBTI, it may in certain cases correspond to ESFp, in other to ESFj in Socionics. SInce most deviations are caused by J/P criterion, which is determined differently in these two theories, in Socionics the last letter is not capitalized. So, if you know your type according to MBTI, you will need to check "bordering" socionic types.
Too complicated, you will say. MBTI gives me a reliable description of my type, why do I need socionics? But MBTI achieved an easy methodology of testing at the cost of neglecting some essential factors of Jungian personality types. Just reckoning with these factors allowed Socionics to create a system of intertype relationships."