To calculate exact count per interval IOA, divide intervals with identical observer counts by all matched intervals compared and multiply by 100. Preserve the two counts for every interval. Exact count agreement treats a difference of one event the same as a larger mismatch for the interval, so pair the percentage with discrepancy patterns and event prevalence.

Define a matched interval

Both observers need the same time boundaries, exposure, response definition, and valid observation state.

Count exact matches

An interval agrees only when the observer counts are identical. Keep discrepancy size separately.

Report prevalence

Show how many intervals contain events and how many are joint zeros. Many empty intervals can inflate the result.

Compare with another view

Mean count-per-interval or event matching may explain the magnitude or location of disagreement.

Build the exact-match table before summarizing

Store the two observer counts for every matched interval and add a simple exact-match flag. Keep intervals observed by only one person, intervals with incompatible boundaries, and intervals invalidated by a recording problem outside the agreement denominator while retaining them in planned coverage.

For each mismatch, record the signed and absolute count difference. Exact count agreement deliberately ignores magnitude in its numerator, so a one-event disagreement and a four-event disagreement each contribute one nonmatch. The discrepancy fields preserve information needed for retraining or definition review.

Separate exact agreement from prevalence

Joint-zero intervals count as exact matches under this method. Report how many of the four matches are joint zeros and how many contain events. When empty intervals dominate, add an occurrence-focused or count-ratio view so the headline percentage does not imply strong agreement on event occurrence.

The choice of interval length also matters. Larger intervals can make counts less likely to match exactly, while very short intervals can create many joint zeros. Retain the interval specification and explain why it fits the event rate and decision.

Use the formula and units for Keiko

For Keiko's exact count-per-interval IOA worksheet: exact count-per-interval IOA = intervals with identical counts / matched intervals compared × 100. Keep observer records independent until both are locked. Preserve the matched exposure, raw observations, numerator, denominator, unrounded calculation, and final rounding.

Work the arithmetic for Keiko

Keiko's observers score six intervals. Their counts match exactly in four and differ in two. Exact count-per-interval IOA is 4 / 6 × 100 = 66.7%. The review then shows that one mismatch differs by one event and the other by four, a distinction the percentage does not contain.

The two mismatch magnitudes sum to five events, but that total cannot reveal which observer recorded more in each interval or calculate another IOA method without the six raw count pairs. The worksheet therefore preserves the pairs instead of reconstructing them from the 66.7% summary.

Apply exact interval count agreement to the decision

Keiko's qualified clinician identifies the decision before choosing an agreement method or threshold. Compare a stricter or complementary method when prevalence, totals, or aggregation could hide relevant disagreement. Repair definitions, visibility, training, sampling, or matching before judging the implementer or client data.

Audit observer and sample conditions for Keiko

Keiko's record identifies observers, independence, training, recording mode, shared exposure, response definition, procedure version, observation coverage, missing pairs, reactivity, and disagreements. Consent, privacy, recording, employment, supervision, and payer rules remain separate requirements. Keep every open pair visible with an owner and next action.

Protect client access during Keiko's observation

Keiko's observation keeps AAC, interpreters, mobility, food, water, bathroom use, prescribed care, health support, rest, relationships, and emergency help available. Do not create extra distress or remove ordinary supports to obtain an agreement sample. Record when access, health, withdrawal, or observer presence changes the condition.

Ask five IOA questions for Keiko

Use these questions in the exact count-per-interval IOA worksheet:

  • Did both observers independently score the same exposure, unit, definition, and condition?
  • Which calculation, numerator, denominator, prevalence, and rounding reproduce the result?
  • Which disagreements, missing pairs, invalid units, reactivity, or matching problems remain?
  • Which validity, treatment-integrity, client-outcome, experience, and access questions stay separate?
  • Which repair, complementary method, next sample, owner, and review date follow?

Keep raw observer records and disagreement types available.

Use current sources within their scope for Keiko

For Keiko's exact count-per-interval IOA worksheet, the BACB ethics hub points to current professional ethics materials. The CASP public summary provides high-level autism-treatment scope without licensed detailed procedures. The BACB Ethics Code addresses competence, client involvement, consent and assent when applicable, documentation, risk, supervision, and evaluation for covered behavior analysts. The BCBA Test Content Outline includes measurement, reliability, sampling, and data-based decisions as examination content rather than a case protocol.

For Keiko, Vollmer, Sloman, and St. Peter Pipkin discuss practical implications of data reliability and treatment-integrity monitoring. Essig, Rotta, and Poling review IOA and fidelity reporting in an identified ABA research corpus. Reed and Azulay describe a calculation tool and agreement methods. ASHA says AAC users should always have access to their tools or devices. These sources do not create one universal IOA method or threshold.

Close Keiko's agreement review

Ask Keiko and the responsible clinician to review the exact count-per-interval IOA worksheet through accessible communication. Record the method, arithmetic, sample, disagreements, limits, measurement repair, selected decision, next observation, and review date. Reopen the analysis when the definition, observer, system, exposure, prevalence, client access, procedure, or decision changes.

Clinician release checklist

  • Are all six intervals matched on time, exposure, definition, and validity?
  • Can another reviewer reproduce four exact matches and two mismatches from raw pairs?
  • Are one-event and four-event discrepancies visible instead of collapsed into one label?
  • Are joint-zero matches and event-containing matches reported separately?
  • Is the 66.7% result interpreted with prevalence, interval length, coverage, and the clinical question?

Related resources

Sources