When my Chromebook charger is plugged into the outlet, it gives me very brief but stinging shocks if I happen to I touch the track-pad and the surrounding metal simultaneously. The shock is delivered by the adjacent metal.
I've checked the three-prong outlet using a circuit tester. I put the red wire prong into the smaller slot and the black wire prong into the larger slot and it lights up. Move the black wire prong to the middle grounding hole and it lights up. Move the black wire prong to the decorative metal escutcheon plate and it lights up. I don't know if the wires inside the wall are properly connected but the tester's behavior indicates a proper ground, if I understand correctly.
What further steps can I take to troubleshoot and fix this?