Fit Curve Model Formulas provides the formulas for the models on the Fit Curve red triangle menu.
 Model Formula Polynomials  where k is the order of the polynomial. These models can also be fit using the Fit Model and Fit Y by X platforms. Logistic 2P  a = Growth Rate b = Inflection Point Logistic 3P  a = Growth Rate b = Inflection Point c = Asymptote Logistic 4P  a = Growth Rate b = Inflection Point c = Lower Asymptote d = Upper Asymptote Logistic 5P  a = Growth Rate b = Inflection Point c = Asymptote 1 d = Asymptote 2 f = Power Gompertz 3P  a = Asymptote b = Growth Rate c = Inflection Point Gompertz 4P  a = Lower Asymptote b = Upper Asymptote c = Growth Rate d = Inflection Point Exponential 2P  a = Scale b = Growth Rate Exponential 3P  a = Asymptote b = Scale c = Growth Rate Biexponential 4P  a = Scale 1 b = Decay Rate 1 c = Scale 2 d = Decay Rate 2 Biexponential 5P  a = Asymptote b = Scale 1 c = Decay Rate 1 d = Scale 2 f = Decay Rate 2 Mechanistic Growth  a = Asymptote b = Scale c = Growth Rate Gaussian Peak  a = Peak Value b = Critical Point c = Growth Rate Lorentzian Peak  a = Peak Value b = Growth Rate c = Critical Point One Compartment Oral Dose   a = Area Under Curve b = Elimination Rate c = Absorption Rate Two Compartment IV Bolus Dose   α = β = a = Initial Concentration b = Transfer Rate In c = Transfer Rate Out d = Elimination Rate Michaelis-Menten  a = Max Reaction Rate b = Inverse Affinity
The Test Parallelism option provides an analysis for testing if the fitted models between groups have the same shape, but are shifted along the X-axis (Parallelism Test). In the Bioassay example, the curve for drug formulation B is shifted to the left of the other three curves. However, you do not know whether the curves still have the same shape (are parallel), or if formulation B is different. The Parallelism Test tells us if the shapes for the different drug formulations have similar shapes and are shifted along the horizontal axis. Select Test Parallelism from the fitted model’s red triangle menu to add the report.
Parallelism Test
Gives the relative potency for each level of the grouping variable. The relative potency is 10^(EC50), where EC50 is the concentration at which the response half way between baseline and maximum is obtained. For the Logistic 2P, 3P, and 4P, the relative potency is 10^(inflection point parameter).
Relative Potencies by group
In the Relative Potency versus standard panel from Relative Potencies by group, note that the relative potencies for drug formulations A and C are nearly one. This indicates that their potencies are similar to that of the standard formulation. The potency for drug formulation B is lower than that of the standard. This means that drug formulation B increases in toxicity as a function of concentration faster than the standard.
Parameter Comparison for Growth Rate Estimates
The Equivalence Test report gives an analysis for testing the equivalence of models across levels of the grouping variable (Equivalence Test). After selecting the option, you specify the level of the grouping variable that you want to test against every other level. There is a report for every level versus the chosen level. Select Equivalence Test from the fitted model’s red triangle menu to add the report.
If all of the confidence intervals are inside the decision lines, then the two groups are practically equal. If a single interval falls outside the lines (as shown in Equivalence Test), then you cannot conclude that the groups are equal. The inflection point for drug formulation B is lower than the standard, which agrees with the previous findings.
Equivalence Test