Science Officer

The Science Officer position is held by the smartest person on board a starship. Note that it is not necessary to be the most persuasive person aboard. Take for example the late Mr. Masada: his readings were completely ignored by Commodore Decker and we know what happened there. (TOS: "That's Right, Guv, Chunks of the Planet Are Being Carved Out By That Really Big, Really Scarey Machine")
Nor is the science officer required to be all that helpful. The Starfleet Manual of Science Officering recommends the following responses to questions put by the Commanding Officer:
;Speculation:I have none, Captain. Insufficient data.
;Give me an update.:No analysis due to insufficient information.
;Then kindly tell me what happened to the stars.:Unknown, Captain.
;Boundary layer between what and what?:Between where we were and where we are.
;We need a formula. We've got to risk implosion!:It's never been done!
;We've got to risk implosion. It's our only chance.:It's never been done.
;Position report.:Impossible to calculate.
There is another line of thought suggesting that the Science Officer should innundate the listener with so much information that decision becomes impossible. See how Mr. Data uses this technique: "Ah, to seek covertly, to go stealthily, to slink, slither, creep, skull, pussyfoot, gum...."
It is unknown whether being a Science Officer interferes with acting as the First Officer or the other way around. Either way, it is not required to explain anything even when the Captain asks for an explanation.