Interrupted intervals ABA data need predefined rules for safety pauses, activity transitions, lost visibility, technical failures, and late observation. Mark each interval as valid-positive, valid-negative, invalid, or missed. Calculate the outcome only from valid intervals and report valid divided by planned coverage separately. A service interruption or missing view should never become client nonoccurrence by default.

Write interruption rules before observing

Define the interval procedure, response rule, interval length, observation period, and states before collection begins. State which events leave an interval valid, which stop observation, which make the score invalid, and which fall outside planned exposure. A brief activity transition may remain observable under one protocol, while loss of visibility, a safety response, or a technical failure may make the interval unusable.

Lina's worksheet uses positive, negative, invalid, missed, and outside-exposure states. It also records the interruption reason, start and end time, observer action, and whether observation resumed. The state definitions are part of the procedure version, so they cannot change quietly after the result is known.

Keep every planned interval in the audit trail

Use one row per planned interval with its scheduled boundary, observed state, positive or negative result when valid, reason when invalid or missed, source record, observer, and context. This preserves the original denominator even when the outcome percentage uses valid intervals. Do not delete an interrupted row or renumber the later intervals.

Separate safety pause, lost visibility, client-requested break, equipment failure, observer delay, setting change, and administrative interruption. These reasons can have different clinical and system implications. Restrict sensitive narrative to the appropriate record while keeping the general measurement state available for reconciliation.

Calculate outcome and coverage separately

Lina has 12 planned intervals. One interval is invalid because observation pauses for safety, and one is invalid because visibility is lost. Ten intervals remain valid. Seven valid intervals are positive and three are negative.

Sampled outcome:

7 positive / 10 valid × 100 = 70%

Valid coverage:

10 valid / 12 planned × 100 = 83.3%, rounded to one decimal place.

The report needs both values. Seventy percent describes the selected interval procedure among valid observations. Coverage shows that two of the 12 planned intervals could not contribute to that result. Scoring those two as negative would produce 7 of 12, or 58.3%, and would incorrectly attribute system or safety interruptions to Lina.

Handle safety and access first

Immediate safety action, health support, communication, and basic needs take priority over completing an interval. The observer should follow the active response plan, then document the measurement state when safe. Never delay help to preserve coverage or a cleaner time series.

Maintain AAC, interpreters, mobility supports, food, water, bathroom access, prescribed care, rest, relationships, and emergency help. ASHA supports continuous AAC access. An interruption caused by unavailable communication or an inaccessible setting belongs in the system record and may limit the sample.

Review missingness and representativeness

Examine whether invalid or missed intervals cluster by activity, time, setting, observer, response intensity, technology, access need, or health condition. Missingness tied to the target or context can bias the sampled result. A high coverage percentage does not prove representative sampling when the omitted intervals are systematically different.

If no intervals are valid, the outcome percentage is undefined even though planned exposure and reasons can still be reported. If only one or two intervals remain, show counts rather than a stable-sounding percentage. Predefine whether collection resumes in the next scheduled interval, restarts a partial interval, or ends for that observation.

Graph states without hiding interruptions

Display positive and negative valid intervals in time order and mark invalid or missed units with a distinct symbol. Do not connect across an interruption as if continuous observation occurred. A companion table can show planned, valid, positive, negative, invalid, missed, coverage, and procedure version by session.

Pritchard and colleagues and Wirth and colleagues examine accuracy and decision implications of discontinuous measurement. Lobo and colleagues provide broader single-case measurement and analysis context. Use the graph and source states to decide whether another sample or a different method is needed.

Use transparent report wording

Lina's sampled outcome was positive in 7 of 10 valid intervals, or 70%. Ten of 12 planned intervals were valid, for 83.3% coverage. One safety pause and one visibility loss were retained as invalid intervals and were not scored as nonoccurrence.

Add interval length, response rule, observation dates, phase, setting, rounding, and missingness pattern. Avoid saying that the response occurred for 70% of time unless the selected procedure and language genuinely support that interpretation.

Keep professional sources in scope

The BACB ethics hub and CASP public summary provide professional context. The BCBA Test Content Outline includes continuous and discontinuous methods, validity, reliability, and representative measurement as examination content. These sources support careful procedure design without supplying a universal missing-interval rule or required coverage threshold.

Clinician review checklist

For interrupted intervals ABA data, confirm the decision question, response rule, interval procedure, interval length, planned exposure, state definitions, valid denominator, positive and negative counts, invalid and missed reasons, coverage arithmetic, outcome arithmetic, rounding, safety actions, access conditions, graph, report wording, client perspective, qualified decision owner, resampling plan, and review date. Preserve the original planned cohort.

Limits of interrupted-interval data

A valid-interval percentage is a sampled, procedure-specific result. It does not recover what occurred during invalid or missed intervals, establish exact count or duration, prove representative measurement, show treatment integrity, demonstrate benefit, or identify cause. Excluding interrupted intervals can bias the result when missingness is systematic. Report coverage and reasons, inspect the pattern, and consider continuous or redesigned measurement when the missing data undermine the decision.

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