Linearity Calculator
Get slope, intercept, r, R², residuals and the y-intercept as a percentage of the target response, with a regression chart.
- ICH Q2(R2)
- Replicates per level
- Residuals table
- No sign-up
Four steps, or fewer
- Set your acceptance criteria and the target (100%) concentration.
- Paste the concentration levels with up to three responses each.
- Check r, the intercept and the residuals. Large or patterned residuals suggest non-linearity even when r is high.
Not sure what to enter? Press Load example to see the calculator with realistic data. Your inputs are saved in this browser, so they are still there when you come back.
How linearity is evaluated
r = Σ(x − x̄)(y − ȳ) / √[Σ(x − x̄)² Σ(y − ȳ)²]
y-intercept at target (%) = a / (b × target + a) × 100
ICH Q2(R2) recommends a minimum of five concentrations. Typical criteria for an assay are r ≥ 0.999 (or R² ≥ 0.998) and a y-intercept within ±2% of the response at 100%. Always look at the residual plot: r alone does not prove linearity.
References
- ICH Q2(R2) Validation of analytical procedures
- ICH Q14 Analytical procedure development
- USP General Chapter <1225>
These calculators are decision support for orientation and training. They are not validated GMP software, and results must be checked against your approved method, SOP and the current pharmacopoeia or guideline before use in GMP records. Your data is processed in your browser and is not sent to Molgenium.