Entering Data and Updating Graphs

Anatomy of a Line Graph: Axes, Scaling, and Coordinates

Line graphs are the most commonly used format for displaying behavior data in applied behavior analysis. Graphs allow the behavior analyst and technician to visually inspect changes in client behavior over time. When working in home, clinic, or school settings, technicians collect data during sessions and transfer those numbers onto graphs so the entire clinical team can see how the client is responding to intervention.

Every standard behavior graph consists of two main intersecting axes. The horizontal axis is called the x-axis or the abscissa, and it typically represents the passage of time, such as sessions, days, or trials. Measurement units on the x-axis must be clearly labeled, such as session numbers, calendar dates, or school weeks. The vertical axis is called the y-axis or the ordinate, and it represents the measurement of the target behavior, also known as the dependent variable. Measurement units on the y-axis must also be clearly labeled, such as count, rate per minute, or duration in minutes.

The point where the x-axis and y-axis intersect is called the origin. If both axes start at zero, the origin represents the coordinate pair (0, 0). The vertical axis usually starts at zero; however, if a supervisor-approved graph uses a different starting point, it must be clearly marked so readers are not misled. In addition, proper scaling of both axes ensures that changes in behavior are neither visually exaggerated nor visually masked.

A data point represents a specific coordinate pair showing the measured behavior value at a specific point in time. To plot a data point, find the session or date on the horizontal axis and move vertically to the measured value. Before placing the point, make sure your calculations match the required measurement units. To calculate a percentage of correct responses, divide the number of correct responses by the total opportunities and multiply by 100. When plotting rate, check that the count has been divided by the correct observation time and that the result matches the graph's units, such as responses per minute. When plotting duration, verify whether the vertical axis requires recording in seconds, minutes, or hours.