Trend
Trend is the overall direction in which data points on a graph move over time: increasing, decreasing, or showing no clear change (zero trend).
When reading a line graph, trend describes where the data path is heading across a series of sessions within a phase. An increasing (upward) trend means the values are going up, a decreasing (downward) trend means they are going down, and a flat or zero trend means there is no consistent change. Trend can also be described by its steepness: a steep trend shows fast change, a gradual one slow change.
Trend is one of three main features of graphed data, along with level and variability. To judge it, look at the whole set of points in a phase rather than at the last two or three. Sometimes the supervisor draws a trend line through the data to make the direction easier to see. With a lot of bounce, a trend can be hard to identify, and a few more sessions may be needed before a conclusion is drawn.
Whether a trend is good news depends on the goal. An increasing trend in correct responses is desired; an increasing trend in self-injury is a concern. A trend that is already moving in the desired direction during baseline also matters, because it makes it hard to tell whether later improvement was caused by the intervention. RBTs identify trends and report them to the supervisor, who decides what to change.
Example and non-example
| Example | A client's percentage of correct responses goes 40, 45, 55, 60 and 70 across five sessions, an increasing trend. |
|---|---|
| Non-example | Data that stay around 50% from session to session, with points scattered above and below, show variability around a level but no trend. |
Don't confuse it with
| Level | Trend is the direction the data are heading; level is where the data sit on the y-axis. |
|---|---|
| Variability | Trend is the overall direction; variability is how much the individual points bounce around that direction. |
Test yourself
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Question 1Which best describes the trend in these data?
Percentage of trials correct by Session: 1: 20, 2: 30, 3: 35, 4: 45, 5: 50, 6: 60, 7: 70. Phases: Intervention from session 1. Show answer
B: An increasing trend. The data path rises from the first session to the last, so the overall direction, the trend, is increasing.
- A: The data path goes up, not down.
- C: The values change steadily in one direction, so there is a clear trend.
- D: The points rise steadily without large jumps up and down.
Task A.7 · 40-hour curriculum section C
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Question 2This graph shows a behavior targeted for reduction. What do the data show?
Number of tantrums by Session: 1: 12, 2: 11, 3: 9, 4: 8, 5: 6, 6: 5, 7: 3. Phases: Intervention from session 1. Show answer
C: The behavior is decreasing across sessions. The data path falls steadily, which is a decreasing trend, the desired direction for a behavior targeted for reduction.
- A: The values get lower over time, not higher.
- B: The values change steadily from session to session.
- D: The points follow a steady downward path with little bounce.
Task A.7 · 40-hour curriculum section C
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Question 3Which best describes these data?
Number of correct responses by Session: 1: 5, 2: 5, 3: 6, 4: 5, 5: 5, 6: 6, 7: 5. Phases: Intervention from session 1. Show answer
B: Stable, with no trend. The points stay within a narrow band without rising or falling overall, so the data are stable with little or no trend.
- A: The values do not rise across sessions.
- C: The values do not fall across sessions.
- D: The points differ by only one unit at most, which is low variability.
Task A.7 · 40-hour curriculum section C
Answer every question to see your score.
On the RBT exam
This term belongs to task A.7 Identifying trends in graphed data in content area A, Data Collection and Graphing, which is 13 of the 75 scored questions.