Baseline median

Establish baseline of an ordinal outcome

For a within-subjects design, a baseline measure of an ordinal variable is measured using a median and interquartile range. This baseline measure can be used as a descriptive variable or as a control that future observations will be compared against. 

The steps for conducting baseline median statistics in SPSS

1. The data is entered in a within-subjects fashion.

2. Click Analyze.

3. Drag the cursor over the Descriptive Statistics drop-down menu.

4. Click Explore.

5. Click on the categorical outcome variable to highlight it.

6. Click on the arrow to move the variable into the Dependent List: box.

7. Click OK.

The steps for interpreting the SPSS output for baseline median statistics

Here is how to interpret the SPSS output:

1. Look in the Descriptives table, in the Median row. This is the baseline median value for the sample.
Click on the Download Database and Download Data Dictionary buttons for a configured database and data dictionary for baseline median statistics.