Use percentage difference to compare your result to a known or theoretical value
Measurements & Uncertainties - OCR A-Level Physics
$$\text{Percentage difference} = \frac{|\text{experimental value} - \text{accepted value}|}{\text{accepted value}} \times 100\%$$
- Use percentage difference to compare your result to a known or theoretical value.
- If the percentage difference is less than the percentage uncertainty, the result is consistent with the accepted value.
- If the percentage difference is greater than the percentage uncertainty, there may be a systematic errorAn error that shifts all readings by the same amount in the same direction. Cannot be reduced by repeating measurements..
- Example: you measure $g = 10.1 m s^-2$ with 5% uncertainty. Accepted value = 9.81. % difference = (10.1 - 9.81) / 9.81 x 100% = 3.0%. Since 3.0% < 5%, the result is consistent.
Examiner Tips and Tricks
- OCR frequently asks 'Is your result consistent with the accepted value?' You MUST compare the percentage difference to the percentage uncertainty and state a conclusion.
- Simply saying 'it is close' is not enough.