Discontinuous measurement
Discontinuous measurement samples behavior during parts of an observation, using intervals, so it gives an estimate rather than a record of every occurrence.
In discontinuous measurement, the session is divided into equal intervals (for example, 10 seconds or 1 minute) and the observer records whether the behavior met the method's scoring rule for each interval, not how many times it happened. The three main methods are partial interval recording, whole interval recording and momentary time sampling. Results are reported as the percentage of intervals in which the behavior was scored.
These methods are used when continuous measurement is impractical: when behavior occurs at very high rates, when episodes are hard to separate, or when an RBT must collect data while also teaching. A timer, vibrating watch or app usually signals the intervals so the observer does not have to watch a clock.
Because only part of the behavior is captured, every discontinuous method introduces error. Partial interval recording tends to overestimate how much behavior occurred, whole interval recording tends to underestimate it, and momentary time sampling can do either. Shorter intervals usually make the estimate more accurate. The percentage of intervals is not a count and not a duration, so it should never be reported as "the behavior happened 40% of the time" or "40 times". RBTs use the method and interval length that the supervisor specifies.
Example and non-example
| Example | An RBT uses a vibrating timer set to 15-second intervals and marks each interval in which a student's humming occurs at any point, then reports the percentage of intervals scored. |
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| Non-example | An RBT counts every time a student hums during class. That is frequency, a continuous measure. |
Don't confuse it with
| Continuous measurement | Continuous measurement records every instance; discontinuous measurement records only whether behavior met a rule in each sampled interval. |
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| Permanent product recording | Permanent product recording measures an outcome after the behavior; discontinuous methods sample behavior while it happens. |
Test yourself
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Question 1Which of these is a continuous measurement procedure?
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C: Duration recording. Continuous measurement captures every occurrence of the behavior during the observation period. Duration recording times each occurrence from start to end, so nothing is missed; the interval and time-sampling procedures record only a sample.
- A: Partial interval recording only notes whether the behavior happened at some point in each interval, so it samples the behavior.
- B: Momentary time sampling checks the behavior only at the moment each interval ends.
- D: Whole interval recording only notes whether the behavior lasted through each entire interval.
Task A.1 · 40-hour curriculum section C
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Question 2Which of these is a discontinuous measurement procedure?
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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 3Data from partial interval, whole interval and momentary time sampling procedures are usually summarized as:
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A: the percentage of intervals scored. Each interval is scored as an occurrence or a nonoccurrence. The summary is the number of scored intervals divided by the total number of intervals, times 100.
- B: Responses per minute is rate, which needs a count of every response; interval procedures do not count responses.
- C: Average length per response is mean duration, which requires timing each occurrence.
- D: Time from cue to response is latency, a continuous measure.
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.