Line graph
A line graph plots data points for a behavior across successive sessions or days and connects them with lines to show change over time.
The line graph is the most common display in applied behavior analysis. The horizontal x-axis shows time (sessions, days or dates) and the vertical y-axis shows the measure of behavior (count, rate, percentage, duration). Each session's value is plotted as a data point, and points within the same condition are joined by a data path. Vertical phase change lines separate conditions such as baseline and intervention, and each phase is labeled.
Line graphs let the team see level, trend and variability at a glance and judge whether behavior changed when the intervention began. RBTs often enter data and update these graphs after each session, so accuracy matters: the right value on the right date, on the correct axis scale, with no connecting line across a phase change, and with gaps rather than zero for sessions that did not happen.
Line graphs are less suited to comparing totals across separate categories with no time order, which is the job of a bar graph. When a line graph has more than one data path, such as correct responses and prompted responses, a legend or labels should make clear which is which.
Example and non-example
| Example | An RBT adds Thursday's rate of hitting (0.3 per minute) as the next data point on a client's graph and connects it to Wednesday's point, which is in the same intervention phase. |
|---|---|
| Non-example | A graph showing the total number of tantrums for each day of the week as separate columns is a bar graph, not a line graph. |
Don't confuse it with
Test yourself
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Question 1On a standard line graph used in ABA services, what is usually shown along the horizontal (x) axis?
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B: Units of time, such as sessions or days. The horizontal axis shows the passage of time, usually sessions or dates, so the graph shows how behavior changes from one session to the next.
- A: The measured value, such as count or percentage, goes on the vertical (y) axis.
- C: Condition names are written as labels above each phase, not along the horizontal axis.
- D: A criterion is shown, if at all, as a line or note on the graph, not as the horizontal axis.
Task A.4 · 40-hour curriculum section C
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Question 2A client's graph has the vertical axis labeled "Percentage of trials correct" and sessions along the horizontal axis. What does each data point on this graph represent?
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C: The percentage of trials correct in one session. On a session-by-session line graph, each data point shows the measured value for one session, here the percentage of trials answered correctly in that session.
- A: A data point summarizes one session, and this graph shows a percentage, not a count of trials.
- B: The axis label says what is plotted, and it is percentage correct, not prompts.
- D: A running total is a cumulative record; this graph plots each session's percentage separately.
Task A.4 · 40-hour curriculum section C
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Question 3A graph shows two target behaviors, hitting and spitting, across the same sessions. What allows a reader to tell the two data paths apart?
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D: A different marker for each behavior, labeled or in a legend. When more than one data path appears on a graph, each uses its own marker (and often line style) and is labeled so readers know which behavior each path shows.
- A: Phase change lines mark changes in conditions; they do not identify which data path is which.
- B: Both behaviors share the same sessions, so they share one horizontal axis.
- C: Connecting two different behaviors would mix their data into one misleading path.
Task A.4 · 40-hour curriculum section C
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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.