Outlets in bedroom, top outlet is working, bottom outlet is not
In addition to Daniel's comment above about any wall switches in the room with unknown function, I suggest adding one of these 6-dollar outlet tester tools to your DIY bag.  Just plug it in and it will diagnose/report many common issues with wall outlet wiring (just in case.)

Note, if you plug one of these into an outlet that is 'switched' by a wall switch somewhere, then the lights will show the 'open hot' condition which is all three lights out. (I know, it's not intuitave: "no-lights means what?")

So you plug it in and leave it in one of the bottom outlets, then go around flipping only one switch at a time until it shows "off-on-on" which signals "correct."  

Remember (while it is unlikely) it could be that the lower plugs are wired in 3-way so, continue flipping switches one at a time, just to make sure the plug doesn't go on then off again.