A.2 · Data Collection and Graphing

Discontinuous measurement

Compare partial-interval, whole-interval and momentary time sampling with an observation timeline and scoring examples. Review what the percentages of intervals and sampled instants tell you about the observation.

Task A.2: Apply discontinuous measurement procedures

Useful foundations: A.1: Continuous measurement

The rule

Interval methods ask different questions: did the behavior happen at all, throughout the interval, or at the observation instant?

Read the recording method before marking the sheet. Each mark records whether the behavior met that method’s criterion for the interval or sampled instant.

Key terms
Discontinuous measurement
Recording whether behavior meets a criterion during selected intervals or at sampled instants.

What to look for

DistinctionLook forHow to decide
Partial intervalAny occurrence within the intervalMark yes even if the occurrence is brief.
Whole intervalBehavior throughout the entire intervalAny interruption makes that interval no.
Momentary time samplingBehavior at the specified instantIgnore what happened earlier when scoring that instant.

Worked examples

One observation, three recording rules

Each row below is a 10-second interval. Filled segments show humming; the diamond is the end-of-interval check.

Interval 1

Humming: seconds 2–4. Partial: yes · Whole: no · Momentary: no

Interval 2

Humming: seconds 0–10. Partial: yes · Whole: yes · Momentary: yes

Interval 3

No humming. Partial: no · Whole: no · Momentary: no

Interval 4

Humming: seconds 8–10. Partial: yes · Whole: no · Momentary: yes

Partial and whole interval

Score the same observation two ways

An observer watches four consecutive 10-second intervals. In interval 1 the learner hums only during seconds 2–4. In interval 2 humming continues for all 10 seconds. There is no humming in interval 3. In interval 4 humming begins at second 8 and continues through the end. The observer watches continuously.

Relevant facts

  • Humming occurs in intervals 1, 2 and 4.
  • Only interval 2 contains uninterrupted humming from start to finish.

Partial interval: 3 of 4. Whole interval: 1 of 4.

Partial: 75%. Whole: 25%.

Partial interval credits any occurrence; whole interval requires the entire interval. Neither result says that humming occupied exactly that percentage of the 40 seconds.

Momentary time sampling

Look at the instant

Use the same four intervals. At the exact end of intervals 1, 2, 3 and 4, humming is respectively absent, present, absent and present. The plan specifies an end-of-interval check.

Relevant facts

  • The check occurs at each interval end.
  • Humming earlier in interval 1 has already stopped.

Record no, yes, no, yes: 2 of 4 checks.

2 ÷ 4 × 100 = 50% of sampled instants

Momentary recording uses the behavior observed at each of the four designated instants. At the first check, humming has already ended, so record no.

What changes the answer?

Change the recording instruction, keeping interval 1 unchanged.

  • Humming occurs briefly near the start and is absent at the end.

Did humming occur at any time?

Yes: partial interval.

The brief occurrence qualifies.

Was humming occurring at the end?

No: momentary sampling.

The sampled instant contains no humming.

The same observed behavior produces different records because each method defines a yes differently.

Remember

  • Any time, all the time, or at that time: identify the method first.
  • Report the percentage of intervals or checks that met the recording criterion.
Sources for this topic

Reviewed 2026-09-30 · A.2 version 3.