Hmm, interesting question. I mean, I've seen newbies joining factions that - in the past - had the name of a Force using group, thinking that it would improve their chances of being Force Sensitive. However to my knowledge most - if not all - of those people did eventually get tested, and there were Force Users in those factions.
If you are in doubt, try asking one or more veteran players - usually they can be found on IRC (yes, I saw your other post asking about it. It really is recommended to get the most out of interactions in this game) and will know of a few Force Users. So if you ask around, you should get an idea of whether Joe Schmo is really Force Sensitive or not.
"May the Grace of Ara go with you, and His Vengeance be wrought upon your enemies."