Error Propagation For Sum Or Difference — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Error Propagation for Sum or Difference Use when calculating the propagation of uncertainty for quantities combined via addition or subtraction (Z = A + B or Z = A - B). Define the derived quantity Z as the sum or difference of measured quantities A and B. Represent the measured values with their uncertainties: (A ± ΔA) and (B ± ΔB). Calculate the worst-case scenarios: Max(Z) = (A + ΔA) + (B + ΔB) and Min(Z) = (A - ΔA) + (B - ΔB) for addition. Determine the maximum deviation from the mean value, which results in ΔZ = ΔA + ΔB. Errors must be absolute errors (same units as the physical quantities), not relative/percentage errors. The quantities A and B must have the same dimensions. This formula represents the maximum possible error (arithmetic sum), not the statistical standard deviation (quadrature sum). Subtracting the errors when the operation is subtraction (errors always accumulate/add). Applying this rule to multiplication or division (which require adding relative errors).