Count-based IOA includes several methods of data collection and calculation. It requires the target behavior to be measured using frequency. Below are some of the most common methods of count-based IOA.
Total Count
Total count IOA is simple to use and calculate. Two observers collect frequency data on the same behavior during an entire observation period. Percentage agreement is calculated using the smaller number as the numerator and the larger number as the denominator. For example, if one data collector records 7 incidents and a second data collector records 10 incidents, the percentage agreement is 70%.
Mean Count-per-Interval IOA
Mean count-per-interval IOA is measured and calculated in the same way as total count. The difference between mean count-per-interval and total count is the division of the observation period into intervals. In other words, total count is used for each interval of an observation period. The percentage for each interval is averaged together to calculate the final IOA.