Interval Recording: Practical Time Sampling for Busy Classrooms
Interval recording estimates behavior occurrence by sampling across time intervals. It's the most practical method when you can't continuously observe — perfect for teachers managing full classrooms.
Three Types of Interval Recording
Each method answers a different question and has implications for data accuracy. Choose based on your specific behavior and measurement goals.
Partial Interval Recording
Mark "yes" if the behavior occurred at any point during the interval, even for just a moment.
Question it answers:
"Did the behavior happen at all?"
Best for:
Behaviors you want to decrease; capturing any occurrence
Limitation:
May overestimate — behavior counted same if 1 sec or 10 sec
Example: If student called out once in a 30-second interval, mark "+"
Whole Interval Recording
Mark "yes" only if the behavior occurred throughout the entire interval without stopping.
Question it answers:
"Was the behavior sustained?"
Best for:
Behaviors you want to increase (on-task, engagement)
Limitation:
May underestimate — 29 sec of 30 still marked "no"
Example: Student on-task for full 1-minute interval = "+"; off-task for 5 seconds = "-"
Momentary Time Sampling
Mark "yes" if the behavior is occurring at the exact moment the interval ends.
Question it answers:
"Is the behavior happening right now?"
Best for:
Busy settings; most practical and research-validated
Limitation:
May miss brief behaviors that occur between samples
Example: Timer beeps, look at student — on-task at that moment = "+"
Quick Comparison
| Method | Record If... | Tends to... | Best Use |
|---|---|---|---|
| Partial (PIR) | Behavior occurred at all | Overestimate | Decrease behaviors |
| Whole (WIR) | Behavior lasted entire interval | Underestimate | Increase behaviors |
| Momentary (MTS) | Behavior occurring at end of interval | Most accurate estimate | General use, busy settings |
How to Set Up Interval Recording
Choose Your Interval Length
Select interval duration based on behavior characteristics:
10-15 seconds
Brief, discrete behaviors; high-rate behaviors
30 seconds
Moderate behaviors; balance of accuracy and practicality
1 minute
On-task monitoring; sustained behaviors
5 minutes
Low-rate behaviors; classroom scanning
Rule of thumb: Interval should be shorter than typical behavior duration
Select Recording Method
Choose partial, whole, or momentary based on your goal:
Set Up Your Signaling System
You need a way to know when intervals end:
- •Vibrating timer app (silent, discrete)
- •Audio cue through earbud
- •Classroom Pulse interval timer
- •Watch with repeating alarm
- •Visual timer you can see
Create Your Recording Form
Set up a grid with intervals across and dates down, or use digital tracking.
For 30-minute observation with 1-minute MTS: create 30 boxes to mark +/-
Calculate Percentage
After observation, calculate: (Intervals scored + ÷ Total intervals) × 100
Example: 24 intervals with behavior out of 30 total = 80%
Sample Interval Recording Data
Student: Riley K.
Behavior: On-task (MTS)
Interval: 1 minute (30 min observation)
Monday 12/2 - Math Class:
Result: 23/30 intervals = 77% on-task
| Date | + Intervals | Total | % On-Task |
|---|---|---|---|
| Mon 12/2 | 23 | 30 | 77% |
| Tue 12/3 | 21 | 30 | 70% |
| Wed 12/4 | 25 | 30 | 83% |
| Thu 12/5 | 24 | 30 | 80% |
| Fri 12/6 | 26 | 30 | 87% |
| Week Average | 23.8 | 30 | 79% |
Frequently Asked Questions
What is interval recording in behavior tracking?▼
Interval recording divides observation time into equal intervals (e.g., 10 seconds, 1 minute) and records whether behavior occurred during each interval. It provides an estimate of behavior occurrence without requiring continuous observation. Three types exist: partial interval (behavior occurred at any point), whole interval (behavior occurred throughout), and momentary time sampling (behavior occurring at the exact moment the interval ends).
When should I use partial vs. whole interval recording?▼
Use partial interval recording when you want to capture any occurrence of the behavior — it's good for behaviors you want to decrease because it may overestimate. Use whole interval recording for behaviors that should be sustained (like on-task) — it may underestimate because behavior must occur for the entire interval. Momentary time sampling is most accurate and easiest for busy settings.
What interval length should I use?▼
Interval length depends on the behavior. For brief, discrete behaviors: use shorter intervals (10-15 seconds). For sustained behaviors like on-task: use longer intervals (1-5 minutes). General guideline: the interval should be shorter than the typical duration of the behavior. For high-frequency behaviors, 10-second intervals are common; for on-task monitoring, 1-minute intervals work well.
How do I calculate percentage from interval data?▼
Percentage = (Number of intervals with behavior ÷ Total intervals observed) × 100. For example, if behavior occurred in 18 out of 30 intervals, that's (18 ÷ 30) × 100 = 60%. This gives you a percentage estimate of time the behavior occurred, though accuracy depends on the interval type and length.
What is momentary time sampling and when is it best?▼
Momentary time sampling (MTS) records whether the behavior is occurring at the exact moment each interval ends — like taking a snapshot. It's the most practical method for busy classrooms because you only need to look once per interval. It's most accurate when intervals are short (10-30 seconds) and is research-validated as providing accurate estimates comparable to continuous recording.
Interval Recording Made Easy
Classroom Pulse includes built-in interval timers with customizable alerts and automatic percentage calculations.