GoalTallyQuick answer: A phase change line is a vertical dashed line on a single-case line graph, drawn between the last session of one condition and the first session of the next. Data points are not connected across it, and each phase is labeled at the top, for example Baseline and Intervention. Here you add a phase and set its first session; the line, the break in the data path and the label are drawn for you.
Rules for phase change lines
- Draw the line halfway between two sessions, never through a data point.
- Don't connect the data path across the line. Each condition gets its own path.
- Label each condition above its phase, using the same words as your write-up.
- When a condition repeats, repeat its label (Baseline, FCT, Baseline, FCT) so the reader can see the reversal.
- Keep the same y-axis scale across all phases.
Common single-case designs
| Design | Phases | What the graph needs to show |
|---|---|---|
| AB | Baseline → Intervention | A change in level or trend after the intervention starts. It's the simplest design but can't rule out other explanations. |
| Reversal (ABAB) | Baseline → Intervention → Baseline → Intervention | Behavior changes each time the intervention is introduced or withdrawn. |
| Changing criterion | Baseline, then phases with stepwise criteria | Behavior moves to each new criterion. Name each phase after its criterion. |
| Multiple baseline | The same AB sequence, staggered across behaviors, settings or people | Change happens in each tier only when the intervention starts there. |
GoalTally draws one tier per graph. For a multiple baseline design, make one graph per tier with the same x-axis range and stack them in your document.
How to make a phase change line graph
- Enter the sessions in order, or paste them from a spreadsheet with a Phase column.
- Add a phase change for every condition change and set the session where it starts.
- Name each phase with a short label. Long names wrap onto two lines.
- Check the graph: the dashed lines sit between sessions and the path breaks at each one.
- Download a PNG or a PDF. The PDF can include each phase's mean, range, trend and PND.
Phase changes in Excel vs here
In Excel you split each phase into its own column so the line breaks, then draw the phase line as a shape and add text boxes for the labels (see ABA graph template for Excel). Here, the break, the dashed line and the label all come from one setting, and they move automatically when you add data.
Frequently asked questions
Should phase change lines be dashed or solid?
Dashed vertical lines are the usual convention for condition changes in ABA graphs, and that's what GoalTally draws.
Why is the data path broken at a phase change?
Connecting the last baseline point to the first intervention point would suggest a continuous trend across two different conditions. Breaking the path keeps each condition's data separate for visual analysis.
Can I make a multiple baseline graph?
Make one graph per tier (behavior, setting or participant) with the same axis range, then stack the PNGs in your document. Stacked tiers in a single figure aren't supported yet.
Can a phase have no data yet?
Yes. A new phase starts with the next session you add, and its line and label appear once it has data.
More free graphs and data sheets
Last updated · Written by the MiniTools team.