Relative potency

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

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

3) Back-transform using the same log base as was used for the dose:
RP = 2 ^{Log 2 (RP)}
RP = e ^{Log e (RP)}
RP = 10 ^{Log10 (RP)}

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:

Where:

t_{(n – 3, 0.025)} is the 97.5% percentile of the t-distribution with (n – 3) degrees of freedom

n is the total number of data points in the Test and Reference samples.

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.