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Are you fitting the relative IC50 but expecting an absolute IC50, and so are surprised by the results. © 1995-2025 GraphPad Software, LLC. All rights ...

https://www.graphpad.com/guides/prism/latest/curve-fitting/

Instead you enter the concentration of radioligand and its Kd as constants, and Prism directly fits the Ki of your cold compound. If you want to know the IC50, ...

https://www.graphpad.com/guides/prism/latest/curve-fitting/

Fit the ratio of two IC50 values directly. From the results in step 8, you can compute what you want to know -- the ratio of the two EC50 values. But Prism ...

https://www.graphpad.com/guides/prism/latest/curve-fitting/

Additional output (legacy for old Prism versions). The options here (dose ratios, and Ki from IC50) are available only to be compatible with earlier versions of ...

https://www.graphpad.com/guides/prism/latest/curve-fitting/

This calculator computes EC 80 or EC 90 (etc.) from EC 50. How? 1. Enter EC 50 I will enter: EC 50 as concentration. For 1nM, enter '1e-9'.

https://www.graphpad.com/quickcalcs/ecanything1/

This is not the same as Vmax,which would require a maximal concentration of substrate. Ki is the inhibition constant, expressed in the same units as X. The IC50 ...

https://www.graphpad.com/guides/prism/latest/curve-fitting/

The only difference is that the inhibitory equations fit the IC50 ("I" for inhibition) while the stimulation equations fit the EC50 ("E" for effective). If ...

https://www.graphpad.com/guides/prism/latest/curve-fitting/

Make sure you pick the form of the equation to match the data you are analyzing. The uncertainty in the value of the EC50 or IC50 is usually quite asymmetrical.

https://www.graphpad.com/guides/prism/latest/curve-fitting/

You should average the logEC50 values, not the EC50 values. Since the distribution of EC50s is usually not symmetrical, the mean of the EC50s is not a good way ...

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Relative vs absolute IC50; Fitting the absolute IC50; Incomplete dose-respone curves; Troubleshooting fits of dose-response curves. Dose-response - Stimulation ...

https://www.graphpad.com/guides/prism/latest/curve-fitting/