GoalTallyQuick answer: In partial interval recording you split an observation into equal intervals, commonly 10 or 15 seconds, and mark an interval if the behavior happens at any time during it, even once and briefly. The result is the percentage of intervals scored: scored intervals ÷ total intervals × 100. It's an estimate rather than a count, and it tends to overestimate how much of the time the behavior actually happens.
How to do partial interval recording
- Choose the interval and observation length. 10-second intervals for 10 minutes gives 60 intervals. The sheet prints each interval's end time so you can follow a stopwatch.
- Start a timer and watch the student for the whole interval.
- Mark the box if the behavior happens at any point in the interval. One occurrence is enough; don't mark the same interval twice.
- Count and divide: marked intervals ÷ total intervals × 100.
- Graph % of intervals. On a tablet, the interval timer highlights the current box and beeps at each change.
Partial interval vs whole interval vs momentary time sampling
| Method | Mark the interval when the behavior… | Tends to | Typical use |
|---|---|---|---|
| Partial interval | happens at any time during the interval | overestimate | Behaviors to decrease; brief or frequent behaviors |
| Whole interval | lasts for the entire interval | underestimate | Behaviors to increase, such as on-task |
| Momentary time sampling | is happening at the end of the interval | over- or underestimate; closer with shorter intervals | Longer-lasting behaviors; one adult watching several students |
Choosing the interval length
Shorter intervals give a closer estimate but are harder to score while teaching. Many observations use 5 to 15 second intervals with a timer or audio cue. Keep the interval and the observation length the same each session so the percentages can be compared; the sheet prints both in the key.
Worked example
Off-task behavior was observed for 10 minutes using 10-second intervals, so there were 60 intervals. It occurred during 18 of them: 18 ÷ 60 × 100 = 30% of intervals. That means the behavior happened in 30% of intervals, not that the student was off task for 30% of the time. For the share of time, use duration recording.
Frequently asked questions
Why does partial interval recording overestimate?
An interval is scored even if the behavior lasted one second of it, so a short behavior can make a whole interval count. That's why it suits behaviors you want to reduce: it won't make progress look better than it is.
Can I record more than one behavior?
Yes, up to three. Each box shows letters (A, B, C) to circle, and the summary line gives a percentage for each behavior.
What if I miss an interval?
Mark it as not observed and leave it out of the total. When scoring on screen, lower Intervals observed to match.
Is partial interval the same as interval recording?
It's one of three interval-based methods, alongside whole interval recording and momentary time sampling.
More free graphs and data sheets
Last updated · Written by the MiniTools team.