i just want to point out the danger of associating introversion with social incompetence because the association is a poorly realized stereotype. it is entirely possible and not uncommon for an introvert to be highly socially competent.

introversion and extroversion are more descriptors of how one handles mental energy than ratings of social competence and degrees of shyness.

for example, i can be very social and outgoing at parties, but they completely exhaust me, and i don't like them. i am introverted because i prefer to direct my mental energy in a more inward, reflective way, and any process that impedes that (e.g., a party) can be very exhausting. it has little to do with how well i can handle myself socially.