What is Relative Percent Difference (RPD)?
Relative Percent Difference (RPD) quantifies how much two values differ relative to their average. It is widely used in quality control, laboratory analysis, and scientific research to compare duplicate measurements or track changes over time.
How to Calculate RPD
[\text{RPD} = \frac{\text{Final Value} - \text{Initial Value}}{\frac{\text{Final Value} + \text{Initial Value}}{2}} \times 100]
Where:
- Final Value is the second or follow-up measurement.
- Initial Value is the first or baseline measurement.
The result is expressed as a percentage. Subtract the initial from the final, divide by their average, then multiply by 100.
Calculation Example
An initial measurement of 3 kg and a final measurement of 4 kg:
[\text{RPD} = \frac{4 - 3}{\frac{4 + 3}{2}} \times 100]
Step by step:
- 4 - 3 = 1
- (4 + 3) / 2 = 3.5
- 1 / 3.5 = 0.2857
- 0.2857 × 100 = 28.57
The relative percent difference is approximately 28.57%.