The personality quizzes can be a bit vague, so I have taken about 10 different ones to gauge my type, which was either always INTP or INTJ. However, to really gauge your type, you must undestand your cognitive functions. The descriptions can be a bit broad or too extreme.
From the functions quiz, I have determined that I am an INTP, but have INTJ leanings as I am trying to be more decisive and results oriented like INTJ.
Here are my actual results.
I have a lot of J functions as well as P functions. Perhaps, based on our moods and stage in life, we can gravitate between two personality types. Many experts will say that the INTJs and INTPs process the world and thoughts very differently, and are therefore are indeed different. However, I don't agree that these types are drastically different, but rather have many similairites.
Knowing your true type consists of not only taking multiple tests, especially cognitive functions test, which tend to be less vague than general MBTI Jungian tests, but also reading the description, and being honest about how you actually are naturally, rather than how you want to be. I notice in myself that my lack of time management is indeed a problem in my professional and financial life. It was easier when I was younger and had less responsibilities, but now, I have trouble with it. So, I am trying to become more efficient with my time. I am ambitious, but my time management issues become my obstacle, so I am working on that. Due to this, I sometimes type as INTJ because the qualities of being organized and decisive is more INTJ than INTP. We certainly can learn from other types and should seek to strengten our weakness to reach a healthy place. However, I have learned to not mistake these acquired skills from your natural propensities.
Here is a few cognitive functions quizzes that are quite good. While I get mixed results with regular MBTI quizzes, cognitive skills tests always place me as an INTP with some INTJ leanings. I find the third quiz least accurate of the three, especially because of it's secondary guess of my type. This is because while I employ social skills easily, I am definitely not an E (extrovert), but am rather a moderate to strong introvert. I am polite and friendly due to my experience and upbringing, and like to learn about cultures and discuss intellectual topics with others, but I prefer to be alone 80% of the time.
Please tell me your accuracy of results after taking the quizzes.
http://www.keys2cognition.com/
http://similarminds.com/classic_jung.html
http://cognitivequiz.com/