Momentary time sampling
Momentary time sampling scores an interval only if the target behavior is occurring at the exact moment the interval ends.
The session is divided into intervals, and when each interval ends (often signaled by a beep or vibration), the observer glances at the client and records whether the behavior is happening at that instant. What happens during the rest of the interval is ignored. Results are reported as the percentage of intervals in which the behavior was present at the moment of observation.
Because the observer only has to look at the end of each interval, momentary time sampling is the easiest interval method to use while doing other work, and it can be used to observe several clients in turn. It works best for behaviors that last a while and occur often, such as engagement, in-seat behavior or self-stimulatory behavior that continues for long periods.
Its main limit is that brief or infrequent behaviors are easily missed: if a behavior starts and stops between checks, it is never recorded. The estimate can be too high or too low depending on timing; it does not lean consistently in one direction the way partial and whole interval recording do. Shorter intervals reduce error. The RBT should look exactly at the signal, not a few seconds before or after, so that the sample is fair.
Example and non-example
| Example | Every 2 minutes a watch vibrates, and an RBT looks up to see whether an adult client is engaged with their sorting task at that moment, marking yes or no. |
|---|---|
| Non-example | Marking yes because the client was engaged earlier in the 2-minute interval, though not at the vibration, is partial interval recording. |
Don't confuse it with
| Partial interval recording | Partial interval scores any occurrence during the interval; momentary time sampling scores only what is happening at the end of the interval. |
|---|---|
| Whole interval recording | Whole interval requires the behavior throughout the interval; momentary time sampling checks a single moment. |
Test yourself
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Question 1Which of these is a discontinuous measurement procedure?
Show answer
D: Momentary time sampling. Discontinuous procedures record a sample of the behavior instead of every occurrence. Momentary time sampling looks at the behavior only at the moment each interval ends.
- A: Frequency recording counts every occurrence during the observation period, so it is continuous.
- B: Duration recording times every occurrence from start to end, so it is continuous.
- C: Interresponse time recording times every gap between responses, so it is continuous.
Task A.2 · 40-hour curriculum section C
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Question 2At an adult day program, an RBT checks every 5 minutes whether a client is working on their assigned task at that exact moment and marks yes or no. Which procedure is this?
Show answer
D: Momentary time sampling. Looking at the behavior only at the moment each interval ends and recording whether it is occurring then is momentary time sampling.
- A: Partial interval recording would score an interval if the behavior happened at any point during it, which requires watching throughout.
- B: Whole interval recording would score an interval only if the client worked during the entire interval.
- C: Duration recording would time how long the client worked.
Task A.2 · 40-hour curriculum section C
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Question 3An RBT is using 1-minute momentary time sampling for out-of-seat behavior. During one interval the client is out of their seat for 50 seconds but is seated when the timer signals the end of the interval. How is that interval scored?
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D: Not scored, because the client was seated at the moment of the check. Momentary time sampling scores only what is happening at the moment the interval ends. Because the client was seated at that moment, the interval is not scored, even though they were out of seat for most of it.
- A: Momentary time sampling ignores what happens before the moment of the check, however long it lasts.
- B: Scoring an interval because the behavior happened at any point is partial interval recording.
- C: Requiring the behavior to fill the interval is the whole interval rule; under momentary time sampling only the moment of the check matters.
Task A.2 · 40-hour curriculum section C
Answer every question to see your score.
On the RBT exam
This term belongs to task A.2 Discontinuous measurement in content area A, Data Collection and Graphing, which is 13 of the 75 scored questions.