The final result of an experiment usually depends on the combination of a number of measured properties, each of which has some associated error.

The combined error may be calculated by using either mathematical relationships, or worst case scenarios:

• Mathematical relationships
• Worst case scenarios

  e.g.

  • If y = a / b, where a = 1.2 ± 0.3 kg and b = 7.0 ± 0.6 m³

  • Then y = 1.2 / 7.0 = 0.17 kg/m³

  • Worst case values of y are (1.2 + 0.3) / (7.0 - 0.6) = 0.23 kg/m³ and (1.2 - 0.3) / (7.0 + 0.6) = 0.12 kg/m³

  • The difference between the calculated and worst case values are 0.05 kg/m³ and 0.06 kg/m³

  • Therefore, y = (0.17 ± 0.06) kg/m³