Keep partial, whole or momentary interval methods explicit and graph the percentage of observed intervals in a fictional example.
Define what you are recording
The observer divides a planned period into equal intervals and applies one chosen scoring method. Partial means occurrence anywhere in an interval; whole means throughout it; momentary means at the specified observation instant.
The fictional record observes a defined action during a chosen group activity. Interval length and method must stay stated in the source sheet.
Collect the data consistently
Select one method and fixed interval length before recording.
Keep scored intervals and actually observed intervals together.
Record missed intervals separately; do not score them as absence.
How to complete each data sheet column
Use the stated units and distinguish an observed zero from a missing observation.
Date: Date of this observation. Use YYYY-MM-DD, for example 2026-10-09. Rows are ordered by date; equal spacing on the graph does not represent elapsed calendar time.
Target: Short fictional or de-identified label for the one activity being observed. Use the same target throughout this report; keep its agreed definition in your approved record.
Phase: Optional label for the observation conditions, such as Observation A. A change creates a chart marker; it does not demonstrate a treatment effect.
Occurred intervals: Whole-number count of observed intervals meeting the selected recording rule. For example, 3 occurred out of 10 observed intervals gives 30%.
Observed intervals: Intervals actually observed and scored, not all intervals originally planned. Use a positive whole number; exclude missed or unobserved intervals.
Method: Partial: occurred at any time in the interval. Whole: occurred throughout the entire interval. Momentary: occurred at the designated sampling instant. Keep one method per report.
Notes: Optional observation context or recording limitation. Exclude names, contact details and other identifiable clinical information.
Fictional worked example
These are original fictional observations, not patient records or a treatment recommendation.
Interval observation data sheet
Date
Target
Phase
Occurred intervals
Observed intervals
Method
Notes
2026-01-05
Fictional interval-participation
Observation A
6
10
momentary
Fictional equal intervals
2026-01-07
Fictional interval-participation
Observation A
7
12
momentary
More observed intervals
2026-01-09
Fictional interval-participation
Observation A
5
10
momentary
Same method
2026-01-12
Fictional interval-participation
Observation B
8
12
momentary
Observation B; same interval length
2026-01-14
Fictional interval-participation
Observation B
7
10
momentary
Fictional observation
2026-01-16
Fictional interval-participation
Observation B
6
12
momentary
No mastery conclusion
Review and interpretation
Six of ten observed intervals is 60% of intervals under the chosen method. It does not mean six minutes or 60% of time.
Interval percentage is not an exact percentage of time.
Switching methods breaks a like-for-like comparison.
Unequal interval lengths also change what is being measured.