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Momentary time sampling is a discontinuous measurement procedure in which an observer records whether a target behavior is occurring at a planned observation moment. Rather than recording everything that happens during an interval, the observer uses a brief snapshot at the specified check time.
The RBT Test Content Outline (3rd ed.) lists momentary time sampling as an example in task A.2, which states that an RBT implements discontinuous measurement procedures. For the broader task language and related procedures, go to discontinuous measurement ABA.
To compare this term with related language, visit ABA terms.
These are original study examples for exam preparation. In real services, implementation follows the supervising BCBA's written plan; ask the supervisor to clarify uncertain scoring instructions.
How Momentary Time Sampling Works#
Time sampling is a broad term for observing behavior according to a planned time schedule instead of producing a continuous record of every moment. Momentary time sampling is one type of time sampling. It uses one observation moment per interval or another timing arrangement specified by the plan.
A data collector begins by reading the operational definition of the target behavior. Next, the collector follows the timing arrangement. At each designated check, the collector looks for the behavior and records whether it is present or absent at that moment. Between checks, earlier behavior does not change the score for the planned observation moment.
For example, an RBT may observe independent work during equal intervals. When the timer signals, the RBT checks whether the learner is writing, reading assigned material, or otherwise meeting the written definition of on-task behavior. If the learner meets the definition at the signal, the interval is marked present. If not, it is marked absent.
A momentary time sampling data sheet may use plus and minus signs, yes and no entries, or another notation defined by the plan. The symbols do not determine the procedure. The scoring rule does: behavior is evaluated at the designated observation moment.
Comparison With Other Interval Procedures#
| Procedure | Positive score rule |
|---|---|
| Momentary time sampling | Behavior occurs at the planned observation moment. |
| Partial interval recording | Behavior occurs at any time during the interval. |
| Whole interval recording | Behavior continues for the entire interval. |
| Continuous measurement | Responses or duration are recorded across the observation period. |
Similar-looking grids can represent different procedures. The key is whether the instruction says to check at one moment, record any occurrence, or require behavior for the full interval. For a direct side-by-side comparison, read partial interval vs whole interval vs momentary time sampling.
Momentary Time Sampling Example#
Suppose a plan defines on-task behavior as looking at assigned materials, writing, or reading the assigned text. An observer checks at the end of each of six equal intervals.
| Interval | Behavior during the interval | Behavior at the check | Score |
|---|---|---|---|
| 1 | On-task for most of the interval, then looked away | No | Absent |
| 2 | Off-task for most of the interval, then began reading | Yes | Present |
| 3 | On-task throughout | Yes | Present |
| 4 | Off-task throughout | No | Absent |
| 5 | On-task briefly, then stopped | No | Absent |
| 6 | Began writing before the check and continued | Yes | Present |
There are three present scores out of six observations. The percentage calculation is:
present observations ÷ total observations × 100
3 ÷ 6 × 100 = 50%
This result means behavior was present during half of the scheduled checks. It does not prove that behavior occurred for half of the observation period.
The same grid also shows why momentary time sampling can move in either direction relative to actual duration. In interval 1, behavior happened for much of the interval but was absent at the check, so the snapshot can underestimate time engaged in behavior. In interval 2, behavior was present at the check after being absent for much of the interval, so the snapshot can overestimate time engaged in behavior.
Momentary time sampling does not have one guaranteed error direction. Whether a particular set of observations is above or below actual duration depends on when the behavior occurs relative to the planned checks.
Use the interval recording scorer to practice converting interval entries into a percentage summary.
Momentary Time Sampling for Groups#
Momentary time sampling for groups follows the same snapshot rule while applying it to more than one learner. A written plan might direct an observer to check engagement for a defined group when a cue occurs. At that cue, the observer records which learners meet the target definition.
For instance, a teacher-led activity may have an observation cue at planned times. At each cue, the observer can scan learners in a consistent order and mark whether each learner is engaged according to the definition. The plan should specify the group, target behavior, scan sequence, timing arrangement, and how the observations are summarized.
A group observation is still momentary time sampling when each score reflects behavior at the designated point. Including several learners does not turn a snapshot procedure into continuous measurement.
When a plan instead requires behavior throughout an interval, use the rule for whole interval recording. When it requires a positive score for behavior at any time in an interval, use the rule for partial interval recording.
Practice Questions#
1. An RBT's written plan uses momentary time sampling to measure humming during equal intervals. Which action implements the plan?
A Correct. Momentary time sampling scores humming at the planned observation moment.
B This uses behavior before the signal rather than behavior at the planned check.
C This requires humming for the interval rather than checking at one moment.
D This records a response count rather than a momentary score.
2. During group art, a written plan uses momentary time sampling and defines engagement as drawing on the assigned page. Before the scheduled check, Nia is drawing. At the check, her pencil rests on the table and she is not drawing. What score should the RBT enter?
A Engagement before the cue does not determine the score at the check.
B Correct. Drawing, the behavior defined as engagement in this plan, is absent at the scheduled check.
C The end of an interval does not make a score present by itself.
D The earlier observation does not determine the score at the cue.
3. A written plan uses momentary time sampling for hand raising. During an interval, Lila raises her hand twice, lowers it, and has her hand raised when the timer signals. Which scoring rule justifies the entry for this interval?
A The behavior before the cue is not the scoring rule described by the plan.
B The stem does not state that hand raising fills the interval.
C Correct. Hand raising is occurring when the timer signals.
D Behavior after the cue does not justify the score at that cue.
4. A written plan uses momentary time sampling for hand raising. During one interval, Lila raises her hand several times but lowers it before the timer signal. What should the RBT record?
A Behavior before the signal does not determine the score at the signal.
B The plan calls for a score at the current signal.
C Tallying responses is different from recording the planned snapshot.
D Correct. The behavior is absent when the timer signals.
Try the free RBT practice test.
FAQ
What is momentary time sampling in ABA?
Momentary time sampling in ABA is a discontinuous measurement procedure that records whether a defined behavior is occurring at a scheduled observation moment. The observer scores the snapshot rather than every occurrence during the interval.
What is time sampling?
Time sampling is an observation approach that uses planned times or intervals to gather behavior data. Momentary time sampling, partial interval recording, and whole interval recording use different scoring rules within a time-based arrangement.
Does momentary time sampling overestimate or underestimate behavior?
It can do either. A present score may follow a mostly absent interval, while an absent score may follow an interval in which behavior occurred for much of the time. The timing of behavior relative to each observation check determines the direction for a particular observation.
How do you calculate momentary time sampling?
Count the observations scored present, divide by the total number of completed observations, and multiply by 100. The result is the percentage of scheduled observation moments at which the behavior was present.
What should a momentary time sampling data sheet include?
A data sheet generally includes the target behavior, timing arrangement, observation entries, scoring notation, and a place to summarize results. The written plan determines the specific definition, schedule, and scoring details.