People often mistake confidence for skill. Watch what someone does, not how sure they sound.

Certainty is easy to produce and tells you almost nothing about ability. The person who speaks without hesitation is sometimes the most capable in the room and sometimes just the most comfortable talking, and tone alone cannot tell you which. Results are the only honest measure. Watching takes more patience than listening does, and it is worth the difference.

In your next group, hold off on deciding who knows what until you have seen some work. Ask the quiet person a direct question, and judge the answer rather than the volume.