Rate vs. Frequency of Behavior: What’s the Difference?

I’m often asked, “What is the difference between rate and frequency?” Frankly, I’ve often wondered myself. In the years I’ve been reading behavioral research and writing, I never discovered whether there was a difference between the two behavioral measurement terms, and in the back of my mind, I always figured I must be missing a nuance. So I finally decided to find the answer, by going to the “source.”

In Cooper, Heron, and Heward’s (2007) book Applied Behavior Analysis (considered by many students of behavior to be the “ABA bible”), the authors define both rate and frequency.[1]

From the Glossary:

Frequency: A ratio of count per observation time; often expressed as count per standard unit of time (e.g., per minute, per hour, per day) and calculated by dividing the number of responses recorded by the number of standard units of time in which the observations were conducted… (p. 696)

What came next surprised me:

…used interchangeably with rate.

Then the definition of rate, as follows:

Rate: A ratio of count per observation time; often expressed as count per standard unit of time (e.g., per minute, per hour, per day) and calculated by dividing the number of responses recorded by the number of standard units of time in which the observations were conducted… (p. 702)

And similarly, the definition was followed by this:

…used interchangeably with frequency.

The definition continues with a description of how the ratio is formed, to wit: “…by combining the different dimensional quantities of count and time (i.e., count time). Ratios formed from different dimensional quantities retain their dimensional quantities.”

But for me, the matter was fully settled when I found they ended the definition with this sentence:

Rate and frequency in behavioral measurement are synonymous terms.

So, what is the difference between rate and frequency? In short, Cooper, Heron, and Heward (2007) answer this question unequivocally: in terms of behavioral measurement, there is no difference between rate and frequency.