PGA281: Input drift spec

Part Number:PGA281

Hi Team,

Customer has question about the drift spec we put in the datasheet.

There are 2 separate section - INPUT and SINGLE-ENDED OUTPUT. 

For INPUT: dVos/dT = +/-0.03 + 0.18/G  uV/C (typ)

For OUTPUT: dVos/dT = 0.05                 uV/C (typ)

My question is for the total drift is it better to just add them together to get total drift or use root sum square?

Thanks!

Andrew