Trend Trend refers to the direction of change across data points within a phase (e.g., during baseline or the period of time in which an intervention is being implemented). There are several ways to show a trend. The easiest way is to visually determine what line best “describes” all of the data. You can “draw” this trend line using a program like Microsoft Excel™. If you would rather use a mathematical approach to calculating the trend line, we recommend the chapter on single-subject designs in Applied Behavior Analysis for Teachers (Alberto & Troutman, 2003).
data in the intervention phase, you would see a descending trend. Because our goal is to decrease off-task behavior, the descending trend tells us our intervention is leading to favorable outcomes.
Level Level refers to the mean range of the data points in a given condition or phase. To calculate the mean range of data points in a condition (Horner et al., 2005; Kratochwill et al., 2010): 1. Use the number (frequency, duration, latency) that each data point represents in a given phase and calculate the sum.
Analyzing trends in the data will help determine if behavior change is moving in the desired direction. Ideally, when implementing a behavior reduction intervention, the desired effect would be a decreasing (or descending) trend relative to baseline. In contrast, when implementing an intervention to increase behaviors or skills, the desired effect would be an increasing (or ascending) trend relative to baseline. As mentioned earlier, you will need to collect at least three data points per condition. Identification of a trend requires at least three data points and often may require five or more. It can be difficult to identify a trend when the increase or decrease in behavior is gradual over time.
2. Divide the sum of data points by the total number of data points in that phase.
Let’s look back at Kelly’s off-task behavior (see Figures 6a and 6b). If you were to draw a line that best represents all of the
Identifying the level from one phase to another is an additional element of analysis that can help to determine the magnitude
3. Draw a horizontal line through the phase at the mean point identified. In the following graphical example, the mean frequency identified using the ten baseline data points is 5.5. Identify where 5.5 is on the vertical axis and simply draw a horizontal line across the baseline phase to indicate the mean level of behavior. Now let’s take a look at the intervention phase. The mean of the five data points in the intervention phase is 14.5. From the vertical axis, locate 14.5 and draw a horizontal line at that point across the intervention phase.
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