A brief analysis of the results
What do these results mean?
This poll should not be taken as representative of gamers, or even online gamers, or even EN Worlders. The results represent a self-selected sample of EN Worlders (i.e., those who like to take tests such as this, and are willing to share their results). These results may or may not generalize to larger groups, such as gamers in general.
Dominant patterns
The pattern thus far shows 2 dominant types, INTP (The Thinker) and INFP (The Idealist). There are 3 other fairly common types, INTJ (The Scientist), ENFP (The Inspirer), and ISTP (The Mechanic).
IN_Ps are uncommon among the general populace. Less than 8% of the general populace is an IN_P type (INTP 3.3, INFP 4.4). So why so many IN types here?
Introverts, in this context, are people with a rich inner world. They are more focused on thought than action. Extraverts, on the other hand, are more oriented towards the external world, i.e., other people and material things. Introvert/extravert has nothing to do with one's comfort or tendencies in socialization (i.e., being a wallflower or a party animal). It's not the least bit surprising that D&D would be a far more attractive game to introverts than extraverts. Those with very high E scores would be unlikely to care for fantasy role-playing.
The high N (iNtuitive) score also makes sense among gamers. N types value imagination and creativity, whereas S (Sensory) types are very pragmatic and detail-oriented, and tend to work step-by-step. N types think in terms of theory and patterns. D&D is a game of creativity, particularly for DMs.
Why are some of the more common types so underrepresented?
Nurturers (ISFJ) and Caregivers (ESFJ) are two of the most common personality types, but greatly underrepresented in this sample. These two types show a significant gender effect, with far more females than males falling into these groups. (ISFJ 19.4% of females, 8.1% of males; ESFJ 16.9% of females, 7.5% of males.) This also holds true for ISFPs (The Artist) and ESFPs (The Performer), but with a much smaller gender split.
Thus, part of the reason for this is the extremely low number of females in the sample. (I am assuming this based on the low number of female board members compared to male board members, since the poll data does not include information on gender.) Note, however, that even though most Nurturers and Caregivers are female, male Nurturers and Caregivers are still more common in the populace than Thinkers and Idealists. I attribute the remaining difference to the conclusions above, on why IN types are drawn to D&D.
Threats to Validity
This isn't how data is normally collected, because there are a number of potential confounding factors here. It's well-known that expectations have a significant effect on performance, so data is best collected "blind." Those conditions are not controlled here. For example, someone who read the thread first, then took the test and voted, may have been significantly influenced by what they read. The extent of this factor is unknown in this sample.
It's also interesting that there's such a dominant IN pattern, since the test in question allows for 50/50 splits, and in case of split, has the ES type as default. Thus, an I/E type with a 50/50 split is assigned an E type by default, despite the fact that they're not really E's. People don't necessarily fit squarely into one type, even though that's how they're treated for purposes of this data. This just adds to the strength of the IN pattern.
Who the heck is this guy and does he know what he's talking about?
I'm a graduate student in Clinical Psychology, working on my doctorate of psychology. I am trained in the administration and interpretation of tests such as the MBTI, although this isn't my area of specialty. I passed my diagnostic CCE (clinical competency evaluations in testing) a couple years ago. But yes, I know what I'm talking about.