Baseline
Baseline is a condition in which the target behavior is measured repeatedly before the intervention is introduced, giving a standard to compare against.
Before an intervention starts, the team needs to know what the behavior looks like under current conditions. During baseline, the behavior is measured with the same definition and procedure that will be used later, usually across several sessions until the data are stable or show a clear pattern. Baseline does not have to mean no teaching or no consequences at all; it means the specific intervention being evaluated is not yet in place.
Baseline data serve several purposes. They show how serious the problem is or how much of a skill the client already has, they can reveal patterns that guide the supervisor's plan, and they provide the comparison for judging whether behavior changes once intervention begins. On a graph, the baseline phase is labeled and separated from intervention by a phase change line.
RBTs collecting baseline data must follow the baseline procedure exactly and avoid adding prompts, extra reinforcement or new strategies, even with good intentions. Doing so changes the baseline and makes later comparison misleading. Baseline is also one of the common phases of an intervention, along with intervention, generalization and maintenance.
Example and non-example
| Example | For five sessions before a token system begins, an RBT records the number of math problems a student completes during 20 minutes of independent work, using the usual classroom routine. |
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| Non-example | Recording the number of problems completed during the first week of the token system is intervention data, not baseline. |
Don't confuse it with
| Phase change line | Baseline is a condition; the phase change line marks where that condition ends on the graph. |
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| Level | Baseline is a phase of the program; level is a feature of the data within any phase. |
Test yourself
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Question 1How many sessions of baseline data are shown on this graph?
Number of hits by Session: 1: 6, 2: 7, 3: 5, 4: 6, 5: 3, 6: 2, 7: 2, 8: 1. Phases: Baseline from session 1, Intervention from session 5. Show answer
C: 4. Baseline runs from the first session up to the phase change line, which falls after the fourth session.
- A: This undercounts; four data points appear before the phase change line.
- B: The fifth point is the first point of the intervention phase.
- D: Eight is the total number of sessions across both phases.
Task A.4 · 40-hour curriculum section C
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Question 2The supervisor tells an RBT that intervention will begin at the next session. Where should the phase change line go when the RBT updates the graph?
Show answer
B: Between the last baseline and first intervention sessions. A phase change line is placed in the space between the final session of one condition and the first session of the next, with a label for the new phase.
- A: The line goes between sessions so that no data point sits on it.
- C: Placing the line on a data point makes it unclear which condition that session belongs to.
- D: The line marks when conditions changed, which is after baseline ends.
Task A.4 · 40-hour curriculum section C
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Question 3What is the purpose of the condition labels written at the top of each phase on a graph?
Show answer
B: They name the condition in effect in each phase. Condition labels, such as "Baseline" or "Intervention," tell the reader which condition was in place for the sessions in that phase.
- A: Labels name conditions; they do not report totals.
- C: Dates or session numbers appear along the horizontal axis.
- D: The label names the condition, not the criterion.
Task A.4 · 40-hour curriculum section C
Answer every question to see your score.
On the RBT exam
This term belongs to task A.4 Entering data and updating graphs in content area A, Data Collection and Graphing, which is 13 of the 75 scored questions.