RSD%, Accuracy & Precision – Technical Guide

Precision

Repeatability (same conditions)
Reproducibility (different conditions)

Relative Standard Deviation (RSD%)

RSD% = (Standard Deviation / Mean) × 100

Example:

Mean = 1.25

SD = 0.015

RSD% = (0.015 / 1.25) × 100 = 1.2%

Accuracy

Closeness to true value
Verified using certified reference materials
Bias calculation required

Accuracy Formula

% Recovery = (Measured / True Value) × 100

Common Lab Mistakes

Confusing precision with accuracy
Ignoring systematic bias
Not recalculating RSD after maintenance