A TV consumer reporter is recording the number of free classes (kickboxing, cycling, etc.) offered at each of the different gyms throughout the city. What are the "experimental units" in this situation?

The gyms

Explanation:

Experimental units -

It refers to the small unit which is considered for any experimental or testing purpose, is referred to as experimental units.

Various experiments can be performed on these units, referred to as the experimental units.

Hence, from the given scenario of the question,

Experiments are performed on the gyms, hence gyms are the experimental units,

Number of free classes need to be calculated from the various gyms.