Trend, Level, Variability

Behavior analysts must possess the ability to analyze data. It is one of the most important skills because we rely so heavily on data to guide our interventions. Visual analysis is the mechanism by which we convert graphs to decisions.

Visual analysis is the practice of interpreting graphs by simply looking at them. When we’re looking at graphs, we want to look for three characteristics of the data paths. These are the level, trend, and variability.

When we refer to the level of data points, we’re talking about where the data points are in relation to the vertical axis. In general terms, levels of behavior may be viewed as low, moderate, or high. When comparing data of two clients, one has high levels of behavior and the other has low levels. The client with higher levels of behavior may have data points consistently around 20 instances per session. The client with lower levels of behavior may have data points consistently around 5 instances per session.

Trend relates to the overall direction of the data path on a graph. We typically label trends as increasing, decreasing, or zero. For example, one of our goals as behavior analysts is to design interventions to change frequency or duration of behaviors. If our interventions are successful in reducing behavior, visual analysis of those graphs will reveal a decreasing trend. The opposite will be true when we’re looking to increase behaviors; we hope to see an upward trend. A zero trend is ideal for determining a baseline prior to implementing interventions.

Variability is captured by the range of deviance of the data points around the line. Variability is more difficult than the other characteristics because it requires an examination of the overall picture of the data. One way to help with interpretation is to draw a best-fit line through the data points. If many of those data points are close to the line, variability could be considered low. However, if there are many data points which deviate greatly from that line, then variability is high.

A lot can be gleaned from visual analysis of graphs. Practice the skill of visual analysis every opportunity you have and think about level, trend, and variability. Just quickly visually reviewing a graph can tell you a lot about behaviors, interventions, and effectiveness

Written By:  Brad Winn, BCBA.

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