GraphPad Curve Fitting Guide

Output tab

Output tab

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Output tab

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Summary table

When analyzing several data sets, the results table is rather lengthy. To display key results on a summary table, check the option box to create a summary table and select the variable you wish to summarize. Prism creates a summary table (as an additional results view) that shows the best-fit value of that parameter for each data set, and graphs this table.

Depending on your choices in the dialog, this may be a bar graph or an XY graph. It shows the best-fit value of a selected parameter for each data set on the table. In some cases, you may analyze the summary table with linear or nonlinear regression. For example, the summary graph may show the best-fit value of a rate constant as a function of concentration (obtained from the column titles of the original data). You can fit a line or curve to that graph.

When Prism compares the fits of two equations, it shows only the results for the second equation. Since this may not be helpful, we suggest that you only make summary tables when fitting a single equation.

Number of digits in output

Choose how many significant digits you want to see in the main results table. This is especially useful if you embed the results table on a graph or layout. If you choose to show many digits of precision in the results, you probably should also choose strict convergence criteria on the Diagnostics tab.

For the table of residuals and the curve itself, you can choose a number format by selecting column(s) and bring up the Decimal Format dialog.

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 Prism (so Prism can open files made with older versions). They are almost always unavailable, becoming available only if you select certain equations from the classic equations list.

Since Prism 5, you can calculate a Gaddum/Schild EC50 shift directly, without need to separately compute dose ratios. Similarly, you can fit competitive binding curves directly to determine the Ki for one or two sites, without a separate Cheng-Prusoff calculation of Ki from IC50(1).


1. Cheng, Y. and Prusoff, W. H. Relationship between the inhibition constant (K1) and the concentration of inhibitor which causes 50 per cent inhibition (I50) of an enzymatic reaction. Biochem Pharmacol, 22: 3099-3108, 1973.