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For all NPC types where we know the relative significance of their primary skills (see below), they have been listed in descending order of significance in-game. So for those NPC that we don't know the relative significances of their primary skills (e.g. Managers and Specialists), it is reasonable to assume that they may be in descending order, or of at least equal weighting. For the NPCs with 3 primary skills other than MOs, the average significance of a primary skill is 3.4 and, going down, their average weightings are 44%, 33%, 23% (. Those percentages then being roughly equivalent to 4.5:3.5:2.5), in case an assumption about weightings for Managers or Specialists was of interest.
In Rebirth 3.00, Virtual Seminars were introduced to the game, which allow us to add a star to a Primary Skill of our hired NPC. They are only currently available via Smalltalk from other NPCs and this feature is described in more detail in the official guide to 3.00 here and on this wiki here <edit: they may be obtainable as mission rewards too; needs checking - Snafu>. Virtual Seminars cannot be used to increase a Marine Officer's Boarding Experience, but since Virtual Seminars take some effort to acquire I would suggest that would be a waste anyway.
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