There are different ways of writing uncertainty. The siunitx manual says "In some fields, it is common to give the uncertainty in a number in brackets after the main part of the number... Alternatively, the uncertainty may be given as a separate part following a sign."
Examples:
- 1.234(5)
- 1.234 ± 0.005
Which academic fields use which style in their journal articles? Does it depend on the region? Is there any agreed upon standard?