In casual conversation, and often in bill of materials, tolerances are specified without the qualifier +/- xx%, often because the specific ± character is hard to obtain (especially in legacy UNIX EDA systems) E.g.
100R 1% 0603 resistor
Is there a convention as to whether this should be interpreted as +/- 1% i.e. resistance value from 99.0-101.0 ohms or as a total tolerance, i.e. resistance value from 99.5-100.5 ohms?
The datasheet should specify this of course, but I was wondering if there is a convention in scientific / engineering speech whether unspecified tolerances are one or two-sided?
Edit: To all: I understand that everyone is trying to be helpful but I not asking for how to solve the problem. My question is literally with regard to whether there are any conventions in interpretation, in electronic engineering, of just "1%" as +/-1% or +/- 0.5%.