GraphPad Statistics Guide

Entering data for a t test

Entering data for a t test

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Entering data for a t test

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Setting up the data table

From the Welcome (or New Table and graph) dialog, choose the Column tab.

If you aren't ready to enter your own data, choose one of the sample data sets.

If you want to enter data, note that there are two choices. You can enter raw data or summary data (as mean, SD or SEM, and n).

Entering raw data

Enter the data for each group into a separate column. The two groups do not have be the same size (it's OK to leave some cells empty). If the data are unpaired, it won't make sense to enter any row titles.

If the data are matched, so each row represents a different subject of experiment, then you may wish to use row titles to identify each row.

Enter mean and SD or SEM

Prism can compute an unpaired t test (but not a paired t test, and not nonparametric comparisons) with data entered as mean, SD (or SEM), and n. This can be useful if you are entering data from another program or publication.

From the Column tab of the Welcome dialog, choose that you wish to enter and plot error values computed elsewhere. Then choose to enter mean, n, and either SD, SEM or %CV (coefficient of variation). Entering sample size (n) is essential. It is not possible to compute a t test if you only enter the mean and SD or SEM without n.

Even though you made your choice on the Column tab of the Welcome dialog, Prism will show you a Grouped data table. Enter your data  on the first row of this table.  

Q&A: Entering data for t tests and related tests

Is it possible to define the two groups with a grouping variable?

Some programs expect (or allow) you to enter all the data into one column, and enter a grouping variable into a second column to define which rows belong to which treatment group. Prism does not use this way to organize data. Instead, the two groups must be defined by two columns. Enter data for one group into column A and the other group into column B.

Can I enter data in lots of columns and then choose two to compare with a t test?

Yes. After you click Analyze, you'll see a list of all data sets on the right side of the dialog. Select the two you wish to compare.

Can I enter data as mean, SD (or SEM) and N?

Yes. Follow this example to see how. With data entered this way, you can only choose an unpaired t test. It is impossible to run a paired t test or a nonparametric test from data entered as mean, SD (or SEM) and N.

Can I enter data for many t tests on one table, and ask Prism to run them all at once?

Yes!