Measurement is the backbone of applied behavior analysis. Domain C on the BCBA exam tests your knowledge of measurement concepts, data collection procedures, and data display methods.
Core Measurement Types
Frequency / Rate
- Frequency: Count of behavior occurrences
- Rate: Frequency divided by time (responses per minute)
- Best for: Discrete behaviors with clear start/end points
Duration
- Total time a behavior occurs
- Best for: Behaviors where how long matters (e.g., on-task behavior, tantrums)
Latency
- Time between stimulus onset and behavior onset
- Best for: Measuring response speed (e.g., compliance latency)
Inter-Response Time (IRT)
- Time between consecutive responses
- Best for: Understanding response patterns and schedules
Percentage-Based Measures
- Trials to criterion, percentage correct, percentage of intervals
- Best for: Comparing performance across different opportunity counts
Interval Recording Methods
Whole Interval Recording
- Behavior must occur for the entire interval to be scored
- Tends to underestimate behavior occurrence
Partial Interval Recording
- Behavior occurs at any point during the interval to be scored
- Tends to overestimate behavior occurrence
Momentary Time Sampling
- Behavior is scored only at the moment the interval ends
- Most accurate estimate of duration for high-rate behaviors
Data Display
Line Graphs
Standard for tracking behavior over time. Must include:
- Labeled axes
- Phase change lines
- Data points connected within phases
Cumulative Records
Show running total of responses over time. Steeper slope = higher rate.
Bar Graphs
Used for comparing discrete categories or conditions.
Exam Tips for Domain C
- Know when to use each measurement type
- Understand the biases of interval recording methods
- Be able to read and interpret graphs
- Know the difference between continuous and discontinuous measurement
Practice these concepts with BxM’s Foundation Track, which includes measurement-specific practice questions and data interpretation exercises.