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C.6: Design and apply discontinuous measurement procedures (e.g., interval recording, time sampling).

Free practice questions for this part of the BCBA, with an explanation for every option.

A BCBA wants to measure sustained on-task behavior for a student, with the goal of increasing it. She plans to use interval recording with 15-s intervals. Which method is most appropriate, and why?
  1. A. Partial-interval recording, because it is the most sensitive to any occurrence of on-task behavior.
    Incorrect. Partial-interval scores an interval with only a brief moment of on-task behavior, which overestimates the target and could make the intervention look more effective than it is.
  2. B. Whole-interval recording, because it tends to underestimate behavior, which makes it a conservative measure for a behavior targeted to increase.
    Correct. Whole-interval requires the behavior throughout the interval, so it tends to underestimate. That conservative bias suits a behavior targeted for increase.
  3. C. Whole-interval recording, because it gives an exact measure of total on-task duration.
    Incorrect. Whole-interval is discontinuous and gives an estimate, not an exact duration.
  4. D. Partial-interval recording, because it tends to underestimate behavior.
    Incorrect. Partial-interval tends to overestimate, not underestimate.
A BCBA consulting at a group home wants to evaluate whether a new activity schedule increases resident engagement in the common room. One staff member is available, and up to 10 residents are present at a time. Which procedure fits best?
  1. A. Continuous duration recording for each resident at the same time
    Incorrect. One observer cannot accurately time the engagement of 10 people at once.
  2. B. Partial-interval recording for each resident, rotating every 10 seconds
    Incorrect. Rotating partial-interval recording across 10 people is hard to do accurately and overestimates engagement.
  3. C. Planned activity check (PLACHECK): at set moments, count how many residents are engaged and divide by the number present
    Correct. PLACHECK is a form of momentary time sampling for groups. It is practical for one observer and gives a percentage of the group that is engaged.
  4. D. Event recording of each resident's initiations to staff
    Incorrect. Initiations to staff are a different behavior from engagement in activities, so this measure would not answer the question.
An RBT uses momentary time sampling at the end of every 5 minutes during a 30-minute session to estimate a client's toy play. Continuous video scoring shows the MTS estimates differ from true duration by as much as 30 percentage points. What change would most improve how well the MTS data match true duration?
  1. A. Switch to partial-interval recording with 5-minute intervals.
    Incorrect. Partial-interval with long intervals greatly overestimates duration-based behavior.
  2. B. Record only the first moment of each session, so observations are consistent.
    Incorrect. A single sample per session would be highly unrepresentative of the session as a whole.
  3. C. Shorten the interval between observation moments (e.g., every 30 seconds), which increases the number of samples.
    Correct. MTS error shrinks as the number of samples grows, so shorter intervals between observation moments make the estimates more accurate.
  4. D. Lengthen the interval to 10 minutes so the RBT can pay closer attention at each moment.
    Incorrect. Fewer samples make the MTS estimate less accurate, not more.

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