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Partial interval recording is a discontinuous measurement procedure in which an observer marks an interval positive when a target behavior occurs at any point during that interval. It summarizes whether behavior occurred across time blocks rather than counting every response or measuring exact duration.
Partial Interval Recording in ABA#
In partial interval ABA measurement, the observer watches throughout each interval. If the defined behavior happens once or more during any portion of that interval, the observer records a positive mark. If it does not happen at all, the observer records a negative mark.
The RBT Test Content Outline (3rd ed.) identifies partial and whole interval recording and momentary time sampling as examples under task A.2, which is to implement discontinuous measurement procedures.
Partial interval recording does not mean observing only part of a session. The word partial refers to behavior occurring during part of an interval. A brief event and an event lasting the entire interval both receive the same positive mark.
For a broader comparison of measurement systems, visit discontinuous measurement when you want to distinguish interval procedures from continuous measurement.
How Partial Interval Recording Works#
- Review the written plan. Identify the operational definition of the target behavior, interval length, observation period, and scoring symbols.
- Start the interval timer. Observe the learner throughout the interval.
- Watch for the target behavior. A single occurrence during the block is enough for a positive score.
- Mark the interval at its end. Record positive if behavior occurred at any point; otherwise record negative.
- Repeat for each interval. Continue until the scheduled observation period ends.
- Summarize the data if requested. Divide positive intervals by completed intervals and multiply by one hundred.
A partial interval recording data sheet commonly has a row of boxes, with one box for each interval. The observer records occurrence for the interval, not the number of times behavior occurred within it.
Partial Interval Recording Example#
Suppose an observer tracks hand tapping for five minutes using ten equal intervals. The written plan calls for partial interval recording.
| Interval | Actual hand-tapping duration | Partial interval mark |
|---|---|---|
| 1 | 2 seconds | + |
| 2 | 0 seconds | - |
| 3 | 15 seconds | + |
| 4 | 0 seconds | - |
| 5 | 1 second | + |
| 6 | 0 seconds | - |
| 7 | 0 seconds | - |
| 8 | 3 seconds | + |
| 9 | 0 seconds | - |
| 10 | 25 seconds | + |
Five of ten intervals are positive. The calculation is:
positive intervals ÷ completed intervals × 100
5 ÷ 10 × 100 = 50% of intervals with behavior
The interval percentage describes occurrence by block, not the exact percentage of time behavior occurred. A short occurrence and a long occurrence receive the same positive score when they happen within an interval.
This is why partial interval recording can overestimate duration. An interval containing one second of behavior receives the same positive score as an interval containing much more behavior.
The following are original fictional study examples.
| Scenario | Partial interval example? | Reason |
|---|---|---|
| Behavior occurs for 2 seconds during a 30-second interval; observer records + | Yes | Any occurrence makes the interval positive. |
| Observer records + only when behavior lasts all 30 seconds | No | That is whole interval scoring. |
| Observer checks behavior only when the timer sounds | No | That is momentary time sampling. |
Use the interval recording scorer when you want to check interval-percentage arithmetic after scoring each block.
How to Graph Partial Interval Data#
To graph partial interval data, calculate the percentage of positive intervals for each observation. Put sessions, dates, or observation periods on the horizontal axis. Put percentage of intervals with behavior on the vertical axis. Plot one value for each completed observation according to the written graphing system.
Clear labels help identify the measure. A label such as “percentage of intervals with hand tapping” is more specific than a label showing only a percentage. Partial interval percentages should not be interpreted as exact duration percentages.
Visit entering data and updating graphs when you want practice with recording values on graphs.
Partial Interval vs. Other Measurement Systems#
| Measurement system | Scoring rule | What the result represents |
|---|---|---|
| Partial interval recording | Behavior occurs at any point in a block | Percentage of intervals with behavior |
| Whole interval recording | Behavior lasts for the entire block | Percentage of intervals with full-block behavior |
| Momentary time sampling | Behavior is checked at a selected moment | Percentage of checks with behavior present |
| Frequency recording | Each response is counted | Total number of responses |
| Duration recording | Time behavior lasts is measured | Amount of time behavior occurred |
Read whole interval recording when you need to decide whether behavior must last throughout an entire block. Visit momentary time sampling when a plan calls for checking behavior only at timer signals. The partial interval vs whole interval vs momentary time sampling page helps compare the three discontinuous procedures side by side.
Scoring Pitfalls#
Reading a positive mark as duration. A positive interval confirms that behavior happened sometime during the block. It does not show how long the behavior lasted.
Checking only at the endpoint. Partial interval recording requires observation across the interval. A check only at a selected instant is momentary time sampling.
Counting each instance inside one interval. Frequency data may count separate responses, but partial interval recording gives one occurrence score per interval.
Changing the plan independently. A different interval length or measurement procedure can change how data are interpreted. Use the supervisor's written directions when the plan is unclear.
Comparing unlike percentages. A percentage of positive intervals is different from a duration percentage, response percentage, rate, or accuracy percentage.
The ABA terms hub is useful when you need to compare measurement vocabulary with other ABA concepts.
Practice Questions#
1. During a scheduled interval, Nora calls out for four seconds. Her written plan uses partial interval recording. At the end of that interval, what should the RBT do?
A Correct. Nora's calling out occurred during the interval, so the interval receives a positive mark.
B This requires behavior across the full block rather than during any portion of it.
C This checks behavior at one moment instead of across the full interval.
D This produces a response count instead of an interval occurrence score.
2. Malik's written plan specifies partial interval recording in equal time blocks. The target behavior happens briefly once during a block. Which action should the observer take?
A This would use an endpoint check rather than observation across the interval.
B Correct. One occurrence during the block is enough for a positive partial interval score.
C This requires behavior for the entire block, which is a different scoring rule.
D Counting every response changes the measure from interval occurrence to frequency.
3. Priya's written plan calls for ten partial intervals. She observed the target behavior in five intervals. What should Priya do after the observation?
A The stated observation records interval occurrence rather than separate response totals.
B This would require behavior to fill each block before it could be scored positive.
C Correct. Divide five positive intervals by ten completed intervals and multiply by 100: 5 ÷ 10 × 100 = 50% of intervals with behavior.
D The interval marks do not provide the exact amount of time behavior occurred.
4. During art group, Lena's target behavior appears for two seconds in several intervals. The written measurement plan specifies partial interval recording. What should the RBT do?
A The brief duration does not change the measurement procedure named in the plan.
B This would use checks at selected moments rather than interval observation.
C This requires behavior throughout the full block before assigning a positive score.
D Correct. The stated plan calls for a positive mark when behavior occurs at any time in the block.
5. Dana calculated that 25% of completed intervals were positive during one observation. The written graph uses one percentage point for each observation. What should Dana do next?
A The stated result is a percentage of positive intervals, not a response count.
B Correct. The written graph calls for one percentage value from each observation.
C The scenario identifies one observation value to enter on the graph.
D The stated data are partial interval percentages rather than duration data.
Try the free RBT practice test.
FAQ
What is partial interval recording in ABA?
Partial interval recording is a discontinuous measurement method that divides observation time into equal blocks. The observer marks a block positive if the defined behavior occurs at any point during that block.
Does partial interval recording overestimate or underestimate behavior?
Partial interval recording can overestimate duration because a brief occurrence makes an entire interval positive. Its result should be interpreted as percentage of intervals with behavior, not as an exact percentage of time behavior occurred.
Is partial interval recording continuous or discontinuous?
Partial interval recording is discontinuous measurement. It records whether behavior occurred within each time block rather than measuring every response or every second of behavior.
How do you calculate partial interval recording?
Divide the number of positive intervals by the number of completed intervals, then multiply by one hundred. For example, five positive intervals out of ten completed intervals equals 50% of intervals with behavior.
When should you use partial interval recording?
Use partial interval recording when the supervising clinician's written plan specifies it. The plan should identify the target behavior, interval length, observation period, and scoring expectations.