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Discontinuous measurement ABA procedures sample behavior in intervals or at set moments instead of measuring every response. The BACB RBT Test Content Outline (3rd ed.) tests this under task A.2, which names partial interval, whole interval, and momentary time sampling.
Task A.2 In Plain Language#
This table turns the official task wording into the decision an RBT candidate can rehearse during original practice.
| Official A.2 wording | Plain-language skill | Original practice focus |
|---|---|---|
| Implement discontinuous measurement procedures | Follow the sampling rule on the data sheet, not a general impression of the session. | Choose the rule, score one interval, or identify a scoring error in a practice scenario. |
| Partial interval | Mark the interval if the response happened one or more times during that interval. | Notice that a brief occurrence is enough to score yes. |
| Whole interval | Mark the interval only if the response lasted for the entire interval. | Notice that a brief gap makes the interval no. |
| Momentary time sampling | Mark the interval based on whether the response is occurring at the sample moment. | Notice that earlier or later behavior does not decide the score. |
For the broader sequence of measurement tasks, use the rbt data collection and graphing study guide after this page. That hub keeps A.1 continuous measurement, A.2 discontinuous measurement, A.3 permanent product, graphing, calculation, and reliability tasks in one Domain A map.
How To Practice Task A.2#
The RBT Test Content Outline (3rd ed.) documents A.2 as an implementation task, so original practice should make you apply a scoring rule instead of only naming a term.
- Identify the scoring rule from a data-sheet instruction.
- Score an interval after a short scenario.
- Distinguish interval samples from exact continuous measures.
- Explain why the written rule matters before summarizing a percentage.
After learning the rule names, practice mixed Domain A scenarios with the rbt practice test data collection and graphing. That page is better for seeing A.2 next to calculations, graph trends, and data-quality errors.
The Three Core Rules#
The three A.2 rules differ by when the observer checks behavior.
| Method | Score yes when... | Useful study contrast | Study mistake |
|---|---|---|---|
| Partial interval recording | The response occurs at any time in the interval. | Detecting whether behavior happened during a sampled period. | Treating the score as the exact number of responses. |
| Whole interval recording | The response occurs for the whole interval. | Checking sustained behavior during sampled periods. | Scoring yes after a response happened for only part of the interval. |
| Momentary time sampling | The response is occurring at the sample moment. | Sampling at the end or another specified instant. | Watching the whole interval when the rule says to check one instant. |
The separate partial interval vs whole interval vs momentary time sampling comparison is useful when the rules blur together. Read that bridge when the stem gives the same observation period but changes only the scoring rule.
Worked Scenario#
The example below scores the same observation period three ways so the differences are visible.
A session is divided into six equal intervals. The target response occurs as follows:
| Interval | What happened | Partial interval | Whole interval | Momentary time sampling |
|---|---|---|---|---|
| 1 | Present for the full interval | Yes | Yes | Yes |
| 2 | Briefly present near the start | Yes | No | No |
| 3 | Absent until the exact endpoint | Yes | No | Yes |
| 4 | Absent the entire interval | No | No | No |
| 5 | Present most of the interval, then stops before the endpoint | Yes | No | No |
| 6 | Present only in the middle | Yes | No | No |
From the same six intervals, partial interval gives five yes scores, whole interval gives one yes score, and momentary time sampling gives two yes scores. Those values are not mistakes; each method answers a different sampling question.
Examples And Non-Examples#
This table separates examples of A.2 from similar data tasks that belong elsewhere in Domain A.
| Scenario | Example or non-example | Reason |
|---|---|---|
| The RBT marks yes when hand raising happens at least once during each interval. | Example | The rule samples whether the response occurred during each interval. |
| The RBT marks yes only when engagement lasts from the start signal through the end signal. | Example | The rule samples sustained responding across the whole interval. |
| The RBT checks whether vocal stereotypy is happening when the timer beeps. | Example | The rule samples behavior at a specified moment. |
| The RBT counts every request during a session. | Non-example | Counting every response is continuous measurement, not interval sampling. |
| The RBT counts completed worksheet problems after the session. | Non-example | A lasting work product is permanent-product recording, not live interval scoring. |
Study Mistakes#
A.2 study mistakes come from changing the rule after the observation begins.
- Do not score a whole interval yes because the response occurred for most of the interval; whole interval requires the full interval.
- Do not turn partial interval into a frequency count; a yes interval says the response occurred, not how many times it occurred.
- Do not use momentary time sampling as if every second mattered; the sample moment is the scoring point.
- Do not compare percentages across different interval sizes unless the context supports that comparison.
- Do not change procedures from clinical judgment; real client data collection follows the supervising BCBA's written plan.
Practice Allocation For This Page#
This table distinguishes the official scored-exam domain weight from this page's practice set.
| Measure | Count | Source or purpose |
|---|---|---|
| Official Domain A scored questions | 13 | RBT Test Content Outline (3rd ed.) |
| Official Domain A share | 17% | RBT Test Content Outline (3rd ed.) |
| This page's practice items | 5 | Original A.2 practice for this article |
| Tags used below | 5 A.2 items | Page-level drill, not an official exam allocation |
Practice Questions#
These five original items rehearse task A.2 without using BACB exam content.
1. During circle time, a sheet says to mark yes when Liam is sitting at the exact timer beep, no matter what happened earlier in the interval. Which procedure matches the sheet?
A Correct. Momentary time sampling scores behavior at the specified sample moment.
B Whole interval recording would require sitting for the entire interval.
C Partial interval recording would score yes after any occurrence during the interval.
D Permanent product recording uses a durable result, not a live timer sample.
2. During art, the sheet says to mark yes only when Maya keeps her hands in her lap from the start signal through the end signal. Which procedure matches the sheet?
A Partial interval recording would score yes after any occurrence during the interval.
B Correct. Whole interval recording requires the response for the entire interval.
C Momentary time sampling checks a single specified instant, not the full interval.
D Event recording counts each response and does not use a whole-interval rule.
3. A 10-interval practice grid shows yes under intervals 2, 3, 5, and 8 because the response appeared briefly in each one. What should the RBT remember when summarizing this kind of score?
A A yes mark does not count every separate response inside the interval.
B Brief appearances do not show that the response lasted for the full duration.
C Correct. Interval scores estimate sampled occurrence rather than exact response counts.
D A summary does not override the measurement rule that produced the data.
4. During lunch, Noor looks at a peer for five seconds near the start of a 30-second interval, then looks away. The rule says score yes when the response happens at least once. How should that interval be scored?
A That reasoning fits whole interval recording, not a rule based on any occurrence.
B That reasoning fits momentary time sampling, not a rule based on any occurrence.
C A brief episode still counts when the rule requires at least one occurrence.
D Correct. The interval is scored yes because the response occurred during it.
5. A data sheet says, "score yes if behavior occurs for the entire 20 seconds." During one interval, the behavior happens for 18 seconds. What mark fits the rule?
A Correct. The response did not last for the entire interval.
B A yes mark would require the response across the full interval.
C Counting responses is a different measurement procedure.
D Product recording would require a lasting outcome to inspect later.
FAQ
What is discontinuous measurement in ABA?
Discontinuous measurement in ABA is a set of sampling procedures that record whether behavior met a rule during intervals or at moments. The RBT Test Content Outline (3rd ed.) lists partial interval, whole interval, and momentary time sampling under task A.2.
Is discontinuous measurement the same as continuous measurement?
No. Continuous measurement records every response dimension named in the plan, such as count, duration, latency, or interresponse time. Discontinuous measurement samples behavior using intervals or moments, so the result is an estimate.
Which discontinuous measurement method overestimates behavior?
Partial interval recording can overestimate duration because a brief response can score the whole interval yes. Whole interval recording can underestimate occurrence because any gap makes the interval no.
Should task A.2 practice include clinical decisions?
Task A.2 in the RBT Test Content Outline (3rd ed.) is about implementing discontinuous measurement procedures. For real services, an RBT follows the written plan and seeks supervisor direction when a data rule is unclear.