Mean duration
Mean duration is the average length of each occurrence of a behavior: the total duration of all episodes divided by the number of episodes.
Mean duration per occurrence answers the question "How long does a typical episode last?" To calculate it, the RBT records the duration of each episode, adds them to get the total duration, then divides by the number of episodes. For example, three tantrums lasting 4, 6 and 8 minutes give a total of 18 minutes, and 18 ÷ 3 = a mean duration of 6 minutes.
Mean duration is useful when the plan aims to change how long each episode lasts, such as shortening tantrums or lengthening periods of independent play. Total duration and mean duration can tell different stories: if tantrums become more frequent but much shorter, total duration may stay similar while mean duration drops. That is why many plans ask for both the count of episodes and the duration of each.
Like any average, the mean can be pulled by one unusual value. One 40-minute episode among several 2-minute episodes will make the mean look much higher than a typical episode. The RBT should keep each episode's duration on the data sheet rather than only the summary, so the supervisor can see the whole picture. When there are zero episodes in a session, mean duration cannot be calculated, and the data sheet should say so rather than recording 0.
Example and non-example
| Example | A client engages in independent play 5 times for 2, 3, 3, 4 and 8 minutes. Total duration is 20 minutes, and mean duration is 20 ÷ 5 = 4 minutes. |
|---|---|
| Non-example | Adding the episodes together and reporting 20 minutes is total duration, not mean duration. |
Don't confuse it with
Test yourself
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Question 1A child has three tantrums during a home session. They last 3 minutes, 5 minutes and 2 minutes. What is the total duration of tantrums for the session?
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D: 10 minutes. Total duration is the sum of the durations of every episode: 3 + 5 + 2 = 10 minutes.
- A: 3 is the number of tantrums (and the length of the first one), not the total time.
- B: 3.33 minutes is the mean duration per tantrum (10 ÷ 3), not the total.
- C: 5 minutes is the longest single tantrum, not the total.
Task A.1 · 40-hour curriculum section C
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Question 2A client had three tantrums lasting 2, 4, and 9 minutes. What was the mean duration per tantrum?
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D: 5 minutes. Mean duration is total duration divided by the number of occurrences: (2 + 4 + 9) / 3 = 15 / 3 = 5 minutes.
- A: 15 minutes is the total duration, not the mean per tantrum.
- B: 4 minutes is the median, the middle value, not the mean.
- C: 3 is the number of tantrums, not a duration.
Task A.6 · 40-hour curriculum section C
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Question 3Which summary tells how long a typical episode of a behavior lasts?
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A: Mean duration. Mean duration is total duration divided by the number of episodes, which tells how long an episode lasts on average.
- B: Total duration is the sum of all episodes, not the length of a typical one.
- C: Rate tells how often episodes occur per unit of time.
- D: Percentage of intervals is an estimate from interval recording, not the length of an episode.
Task A.6 · 40-hour curriculum section C
Answer every question to see your score.
On the RBT exam
This term belongs to task A.6 Calculating and summarizing data in content area A, Data Collection and Graphing, which is 13 of the 75 scored questions.