If I said to you something has a 4% margin of error, is that:
a) +4% and -4%
- OR -
b) +2% and -2%
I say it is the latter such that the spread is 4%, correct?
- Jinx
I believe it’s -4% to +4%
it means (-4) to (+4).
google came up with this pdf document. refer page 4.
It could be either depending on the intent of the person that wrote it. But whenever I’m using this method of describing confidence intervals, I mean -4 to 4, and everywhere else I’ve seen it used where I can mathematically derive their intent, the authors intend it that way as well.
It’s a rather inefficient way of describing confidence intervals, a less ambiguous way is to say “with 95% certainty the true value lies between X and Y.” But “4 percent margin of error” is shorter and easier to understand.
It normally means that there is a 95% confidence interval of [x-4%, x+4%].
However, in certain scientific/engineering branches it can mean that the sigma is 4%, which leads to a 95% confidence interval of ±8% (if I’m not misstaken).