GraphPad Statistics Guide

Interpreting results: Multiple t tests

Interpreting results: Multiple t tests

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Interpreting results: Multiple t tests

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The results are presented on two pages.

t tests page

This page shows the t test for each row. The P value for each comparison is shown, and also the multiplicity adjusted P value, which is higher.  

If you chose the statistical significance approach, the first column is  labeled "Significant?" shows an asterisk if this comparison is declared to be statistically significant, after any adjustments you requested for multiple comparisons, and is otherwise blank. This column either contains a single asterisk or not. It never shows several asterisks.

If you chose the FDR approach, then the first column is labeled "Discovery?" and contains an asterisk for those rows deemed to be "discoveries" and otherwise is blank.

Significant results page or Discoveries page

This page only shows the rows whose results meet the definition of a "statistically significant result" or a "discovery" based on your choices in the dialog. The rows are sorted by P value, with the smallest P value on top.

What is n?

In most cases, you have complete data on each row and the number of t tests equals the number of rows, so there is no ambiguity.

In some cases, it may not be possible to compute the t test for some rows (because the SD of the replicates is 0.0, or because there is only one value for each group). Prism only counts the rows for which a t test could be computed. If a t test could not be computed for some rows, Prism points this out in a floating note.