Frequency is a type of continuous measurement. The frequency of a behavior is the number of times the behavior occurs in an observation period.
Let?s look at an example:
Sarah is a teacher. She wanted to monitor the number of times one of her student asked for a break. She constructs a behaviour definition of asking for a break so it is clear what it is to be counted. Each time her student asked for a break, she recorded it on a daily data collection sheet. At the end of the day, she tallied the number of requests for a break and there were four.
In this case, the observation period is one school day ? 5 hours. The number of requests for a break was four. The frequency of requests was four per day.
Let?s look at another example:
Mario wanted to lose weight. He decided to record the frequency of the chocolate bars each day. Each time he ate a chocolate bar, he placed a plus mark in his diary for that day. On Monday, he ate one bar. On Tuesday he ate 3 bars. On Wednesday he ate four
In the previous examples, we looked at frequency per day. However, it is important to understand that frequency can be expressed using any measurement of time ? minutes, hours, days, weeks, months or years.
For example, if you were observing a client?s challenging behaviour, over a three hour period and they engaged in hitting, 4 times during that observation period, you could express that frequency as an hourly rate.
It would be a rate of 1.33 incidents of challenging behaviour per hour.
Such hourly rates are useful when the length of observation periods differs. For example, 20 instances of behavior occurring in a 1 hour session is quite different than 20 instances occurring during a 3-hour session. By converting how you report the behaviour to an hourly rate, you make it easier to make reliable comparisons.
We use frequency measurement when the behaviour of interest has a clear beginning and end point that makes it easy to distinguish between each incident and when the behaviour of interest occurs at a rate where the observer can accurately count it.
When the target behaviour does not have clear beginning and end points, or when it might be difficult for an observer to accurately count every incident of a behaviour, other methods might be more appropriate.