Question

Which of the following formulas correctly represents Relative Precision Index (RPI)?
1. \(\rm RPI = \frac{Work \ tolerance}{\bar{R}}\)
2. \(\rm RPI = \frac{R}{Work \ tolerance}\)
3. \(\rm RPI = \frac{Work \ tolerance}{2}\)
4. RPI = Work tolerance \(\rm \overline{XR}\)

Answer 1

Correct Answer - Option 1 : \(\rm RPI = \frac{Work \ tolerance}{\bar{R}}\)

Explanation:

Relative Precision Index (RPI): It is defined as the interval between the specification limits divided by the mean of the range R of the measured samples.

\(\rm RPI = \frac {USL\ -\ LSL}{R}\)

Where USL = Upper Specification Limit; LSL = Lower Specification Limit; R = Range

∵ Work Tolerance = USL - LSL

∴ \(\rm RPI = \frac {Work\ Tolerance}{R}\)