Hi Debpriya De, Both versions are correct, but I'd say "margin of error" is used much more frequently. I would not view the two as interchangeable, though there are probably some contexts in which you could use either one. A "margin of error" is a fixed expression, and the three words form a single idea.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.