Relative Potency

1) Fit a parallel model to reference standard and test sample pair:

and

2) Calculate Log (RP) = (A_Test - A_Ref) / B

3) Back-transform using the same log base as was used for the dose:

Confidence interval for relative potency

The variance, s², of the estimate of Log (RP) is calculated from the variances and covariances of the model parameter estimates of

and

using the Delta method.

The 95% confidence interval for Log (RP) is then calculated as:

· Log (RP) ± z_0.025 √ s²

Where:

z_0.025 is the 97.5% percentile of the normal distribution.

· The 95% confidence interval for RP is obtained by back-transforming the interval for Log RP using the same log base as was used for the dose.