To enter the logarithm, enter '-9'.This video walks you through the steps required to undertake a t test in Prism. If you enter '1e-9', that is exactly the same as entering '0.000000001'. The reason for this is that the logarithm of zero is not defined. If any of your X values are 0.0, use the option at the top of the dialog to change these to some small concentration. Base 10 (common) logarithms are used most commonly.ģ.

On the dialog, check the option to transform X to logarithms. From the data table, click Analyze and then choose Transform Concentrations (X), which is the second analysis listed on the Analyze dialog.Ģ. If you entered actual doses or concentrations, instead of their logarithms, but want to use an equation that assumes the X values are logarithms, use Prism to transform the X values.ġ. How to transform your X values from concentrations to logarithm of concentrations The X values are still concentrations, not logarithms of concentrations. Stretching the axis to a logarithmic scale does not change the data. If you entered X values as concentrations, they are still concentrations even if you graph those data on a graph where the X axis uses a logarithmic scale. The nonlinear regression part of Prism does not 'see' the graph you made. Note that Prism's nonlinear regression 'sees' a table of XY values, and fits that. It matters a lot that you pick an equation that corresponds to your data. The other set assumes you entered the logarithms of concentration or dose.One set assumes you have entered concentrations (or doses) as X.Prism provides two sets of dose-response equations.

Graphpad prism molarity calculator