I'm 50/50 for each characteristic in the Myers-Briggs tests?

The test aren't all that accurate in determining one's mbti type. Also, nobody will posses 100% of any type's traits. A more efficient way of identifying your main type is to thoroughly study the eight cognitive functions. For a very simplified description of them, look for my posts in these links (ignore the irrelevant info): https://answers.yahoo.com/question/index?qid=20141015142032AA2ra9O https://answers.yahoo.com/question/index?qid=20130824143411AAOV3Wi
As for function order ---> https://answers.yahoo.com/question/index?qid=20140629123919AAZfkbf


If those links don't help, then here are some general descriptions I've gathered from various sources:

Introverts (Ixxx) are more introspective and reflective than extraverts (Exxx). Extraverts are more externally involved than introverts. Introverts spend more time "in their heads" than extraverts. Introverts think first, then act, then think some more. Extraverts act first, then think, then act some more. Extraverts get energized by the outer world. Introverts get energized by their inner world.

Sensors (xSxx) think concretely and rely mainly on their five senses to gather information. Intuitives (xNxx) think abstractly and rely mainly on hunches as a means of gathering information. Sensors tend to perform better on hands-on tasks, while intuitives tend to perform better on hands-off (i.e. mental) tasks.

Thinkers (xxTx) generally make decisions based on facts and impersonal data, unlike feelers (xxFx) who generally make decisions based on morality and ethics.

Because they have a judging function (T, F) as their first extraverted (e) function, judgers (xxxJ) seek closure in the outside world, striving for a structured, decided lifestyle. On the other hand, perceivers (xxxP), who have a perception function (S, N) as their first extraverted function, seek openness in the outside world, striving for a flexible, adaptable lifestyle. Though ironically, judgers have a unorganized inner world, due to having a perception function as their first introverted (i) function, and perceivers have an organized inner world, due to having a judging function as their first introverted function. This is precisely why Js seek stability and Ps seek variability. Js think linearly and Ps think holistically.

Sensing-perceiving (xSxP) types naturally posses excellent attunement and awareness of their tangible surroundings, since they all have strong extraverted (objective) sensing (Se). They are tactile, kinesthetic learners who require physical movement and activity in order to assimilate information, which is why they have difficulty learning in a traditional classroom setting. They do best in situations that require them to be focused in the here-and-now, such as sports. Their idea of having a good time is doing activities that please the senses, experiencing all that the finer, thrilling things the material world has to offer. This is all especially true for the extraverts (ESxP).

Sensing-judging (xSxJ) types are adept at archiving and recalling information, since they all have strong introverted (subjective) sensing (Si). They tend to be traditional, conservative inside-the-box thinkers. Unlike SPs, SJs thrive in the traditional school system. The school system, which basically emphasizes hard work, rote memorization, and rules, was built for and caters to SJs. They are said to be the ones who keep society stable. Their idea of having a good time is enjoying the very simple things in life, reaping the benefits of their contribution to society, and taking a trip down memory lane. They are naturally past-oriented.

Intuitive-thinking (xNTx) types are said to be very rational. Like SJs, they tend to do fairly well in school also. However, unlike SJs, who tend to spit back what the teacher tells them, NTs can synthesize their own information from analysis of the material they learn. NTs tend perform better in subjects that require "higher-level," conceptual thinking, while SJs tend to score better on more straightforward subjects that require excellent retrieval of facts alone. The perceivers (xNTP), who share introverted thinking (Ti), tend to be extremely knowledgeable for its own sake and are the ones who most people call academic geniuses. The judgers (xNTJ), who share extraverted thinking (Te), tend to exhibit an attitude with a pragmatic bent to it, looking for the practical application of their knowledge. They, along with SJs, are the ones who just want to pass to increase the likelihood of success. They want to execute, so therefore value usefulness in information.

Intuitive-feeling (xNFx) types are known as idealist. They are likely to fight for a deeper cause. They are very dreamy and have high aspirations, such as world peace, environmental protection, unconditional love, etc.

Intuitive-perceiving (xNxP) types, having strong extraverted intuition (Ne), tend to have a remarkable, fast-paced intellectual wit to them, which comes from noticing what is missing from an environment. Their idea of having a good time is bouncing quirky ideas off each other and coming up with and discussing fresh, unheard-of innovations. They enjoy thinking outside the box. Although it may seem like they are future oriented, it would actually be more accurate to say that they live in the moment, being P types. They operate in the "now," even if not necessarily fully in the "here."

Intuitive-judging (xNxJ) types see underlying relationships between ideas, unlike NPs who see the ideas themselves. They see the relationships between situations, unlike SPs who see the occurrences themselves. They tend to remember an essence of how an event went, unlike SJs who remember the literal, sensory aspects of an event. They all share strong introverted intuition (Ni), which is very different than Ne. With Ne, multiple ideas are brainstormed from a single one. With Ni, connections and associations are made from multiple ideas, from which the most probable idea is zoomed onto. NJs are naturally future-oriented. Or rather, they view time as a continuous, river-like flow of continuity, as opposed to a division of days like other temperaments do. The idea of a "fresh new day" feels relatively arbitrary in their point of view, especially to the introverts (INxJ). Their idea of having a good time is in seeing their visions manifest in reality.

Sensing-feeling (xSFx) types are said to emotionally mature fast.

Extraverted-judging (ExxJ) and introverted-perceiving (IxxP) types are better at thoroughly processing new experiences and information at the time they are happening because they have a judging function as their dominant function. Extraverted-perceiving (ExxP) and introverted-judging (IxxJ) types are better at soaking in new information and experiences because they have a perception function as their dominant function. Unlike EJs and IPs, they need to set time aside in order to fully process the info, as they process experiences better when "outside" said experiences, after they have occurred.

Intuitive-introverts (INxx) are likely to feel like an alien in this world. They tend to think in ways that deviate from the mainstream, and so are most likely to feel like outcast to society.

***
When I took a few tests I got I(N/S)TJ. But I know I am not an ISTJ because I am certain I don't have powerful Si.
INTJ: https://answers.yahoo.com/question/index?qid=20141011060135AAOnHXH
ENTJ: https://answers.yahoo.com/question/index?qid=20140927183017AAu1dET
(look for my responses)
INTJs have stronger Ni and Fi, ENTJs have stronger Te and Se. Both have strong Ni and Te, and relatively weak Fi and Se. FYI, all mbti temperaments utilize sensing, intuition, feeling, and thinking. The differences between them come from the order and orientation of such.

The primary focus of INTJ (Ni > Te) is in gaining insights and discovering new ways of seeing the world. They use results-oriented, execution-style thinking to back that up. ENTJ (Te > Ni) uses execution thinking to manipulate the environment in accordance to objectives for its very own sake. They back that up using pattern recognition. INTJ is first and foremost an intuitive. ENTJ is first and foremost a thinker.

***
Objective functions involve the outside world, so therefore cannot be argued. Subjective functions are contained within the construct of ones mind, so therefore can be argued. .

- extraverted (objective) sensing - Scans physical environmental for changes that are readily apparent in the here-and-now.
- introverted (subjective) sensing - Filters sensation through subjective impressions of past experience. Compares current environment to the personalized memories. ex: "The last time I went to that restaurant, the waiters were so much better."
- extraverted (objective) intuition - ex: It is readily apparent that there are no pink elephants, flying busses, and levitating mats.
- introverted (subjective) intuition - ex: "Based on the way you are behaving, you seem to be going down a dark path."
- extraverted (objective) thinking - ex: 5 + 5 = 10. The shortest distance between two points is a straight line. As of now, this is the shortest and most efficient way to get this task done.
- introverted (subjective) thinking - ex: "If-then" statements can be argued for validity and soundness.
- extraverted (objective) feeling - ex: the emotional vibe of a group of people
- introverted (subjective) feeling - ex: morals that one derived from his own interpretation of his experiences

Representations of Functions:
http://s1119.photobucket.com/user/swiftslinger/media/797f677f-cefe-4fa6-9f1f-8d76b58f8ac3_zps81afea92.jpg.html?sort=3&o=1
http://s1119.photobucket.com/user/swiftslinger/media/4bffbef9-1995-4b26-a047-929a00771f74_zpsddece4f5.jpg.html?sort=3&o=0

No