Technical definition, clinical ABA application, discriminative non-examples, and test-day traps for behavior analysis candidates.
The degree to which two or more independent observers report the same observed values after measuring the same events. Formula varies by measure: Total Count IOA, Mean Count-per-Interval IOA, Exact Count-per-Interval IOA, and Scored/Unscored Interval IOA.
Two behavior analysts record occurrences of aggression during 10 one-minute intervals. They agree on occurrences in 8 intervals and disagree in 2 intervals, resulting in 80% Scored-Interval IOA.
One observer filming a session and scoring it twice on separate days (this assesses intra-observer reliability, not IOA).
Total Count IOA tends to overestimate agreement because it compares overall session totals rather than interval-by-interval precision.
When measuring a low-rate behavior that occurs in only 10% of observation intervals, which interobserver agreement formula provides the most rigorous, conservative metric of reliability?
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