Whole-interval recording

The response must meet the full-interval rule

Suppose a ten-minute observation uses ten one-minute intervals. If the response lasts 59 seconds and stops for one second, the interval scores negative under a strict full-interval rule. If it lasts throughout the next minute, that interval scores positive.

Define whether brief gaps are allowed. A rule that allows a two-second interruption differs from one requiring uninterrupted occurrence. Store the rule with the data.

Build the observation plan

Specify:

• response onset, offset, and treatment of brief gaps
• observation start and stop events
• interval length and timer source
• recording period and tolerance rules
• eligible intervals and missed-observation states
• prompts, ordinary supports, activities, and settings

The observer generally needs to watch the full interval. A quick check at the endpoint cannot establish whole-interval occurrence.

Calculate the score with its denominator

If the response meets the full-interval rule in 6 of 12 valid intervals, report 6 of 12 whole intervals, or 50%. Keep the six and 12 beside the percentage.

The numerator contains intervals rather than responses or minutes. Twelve one-minute intervals happen to cover 12 minutes, yet the percentage still describes full-interval scores.

A fictional library example

Nadia is a fictional 14-year-old who wants longer periods to read chosen graphic novels at a library club. With Nadia, the team defines engaged reading as looking at or tactually exploring the selected page, turning a page, or communicating about the book. Chosen breaks remain available and receive their own code.

Across a 24-minute observation with two-minute intervals, engaged reading meets the full-interval rule in 7 of 12 intervals, or 58.3%. A separate continuous-duration record shows 19 engaged minutes, or 19 of 24 minutes, 79.2%.

The difference is expected. Several intervals include brief chosen breaks or conversation and therefore score negative even when reading occupies most of the interval. The example describes measurement and supports no causal conclusion.

Whole-interval scores can understate time occupied

Any interruption can turn an interval negative. When readers treat positive intervals as exact duration, the method tends to understate the share of time occupied. Longer intervals create more opportunity for an interruption and can reduce positive scores.

Error depends on the response pattern, interval length, observation schedule, and gap rule. Percentages from 15-second and five-minute intervals are different measurement products.

Choose it for sustained occurrence questions

Whole-interval recording may fit when sustained engagement, availability of a support, or continuous staff implementation across short periods matters and direct duration recording is impractical. It can also serve as a procedural check when every portion of an interval must meet a standard.

Choose duration when exact time matters, event recording when count matters, partial interval when any occurrence matters, and momentary sampling when state at checkpoints is sufficient. Feasibility and expected error should fit the decision.

Separate client and system measures

If materials arrive late, AAC is unavailable, or a partner interrupts the activity, record that condition. A full-interval miss can reflect an environment that made the response impossible.

Keep communication, mobility and sensory supports, breaks, food, water, bathroom access, prescribed care, and emergency help available. Do not withhold a useful support to improve an interval percentage.

Decide how interval boundaries handle transitions

Whole-interval data can change when the observation begins in the middle of an activity or ends during a response. Start after a clear setup event when possible. If the first or last interval is shorter, exclude it under the prewritten rule or label its actual length. Record scheduled transitions separately so predictable activity changes do not appear as unexplained losses of sustained engagement.

Make missed observation visible

Report valid intervals divided by planned intervals. If 12 of 15 planned intervals were fully observed, coverage is 12 of 15, or 80%. Calculate the whole-interval percentage across the 12 valid intervals and list the three missed intervals by reason.

Do not score a partially viewed interval as negative unless that is the predeclared and justified observation rule. A missing interval reflects measurement coverage.

Review reliability and meaning

Useful controls include on-time and fully observed intervals, current definitions, timer failures, exclusions, and sampled observer agreement. Agreement supports consistency and does not prove that sustained occurrence represents a valuable outcome.

Ask the person about comfort, effort, choice, and whether the activity matters. Pair the interval score with duration or another measure when the full pattern affects decisions.

The BACB BCBA Test Content Outline, Sixth Edition covers discontinuous measurement, interval recording, time sampling, validity, reliability, and representative procedure selection. It is examination content and specifies no universal interval length.