"Error range" refers to the possible margin or amount of mistake or inaccuracy in a measurement or calculation. It indicates how far off or uncertain a particular result or data could be. Full definition
The survey margin of error ranged from 4.5 to 4.8 percent. (studentloanhero.com)
Re # 21: I think one of the issues here is «with an admittedly large error range». (realclimate.org)
Also, of course you know that the current numbers are not inconsistent with theory since the difference falls within the predicted error range. (realclimate.org)