The whole Myerrs-Briggs type indicator test is a sham.
And here's why. It only captures one snapshot in time, and that snap shot has relatively low resolution(poor questions).
Now let's make a big assumption, and assume the MBTI test has great resolution (great questions) on Introversion/Extroversion. It can tell exactly how introverted someone is at a PARTICULAR MOMENT IN TIME. Then, the people who made the test, assign you to a unique category.
A whole entire field could be dedicated to the RATES at which human beings travel between introversion an extroversion. You could also look at the relative peaks of introversion/extroversion, and the typical RANGES at which an individual moves in a week, month, year, etc.
However, people aren't doing this. They are just wasting time subjecting people to the MBTI test, once here, once there, and looking at the individual results. And here's the problem with MBTI, it's preventing us from studying someone that's better at understanding people. It's a really simple test and it's being embraced too widely. Studying rates, ranges, and etc would help you predict when your neighbor will transition from ISTJ to ISFJ, how long they are going to stay there, and here's the BIG ONE - what will make them switch.
Maybe it was just my MBTI administrator, but she claimed you are more or less a particular type (ISTJ, etc) from birth. She explained there was some natural movement from one category to another, but we didn't dwell too much on the topic.
It's similar to IQ tests. We're always stressing on a particular person's IQ. Why not stress on IQ change. I would like to work with people who are actively trying to increase their IQ, as opposed to those that are probably on the decline. Further more, isn't it weird how we have to ask different age groups different questions to gauge IQ? Why is this? It's probably because the brain is going through a time period of (relatively) rapid development. But if we keep on testing people's IQ, we're probably going to learn very little about the brain development process.