The average amount of ozone in several cities across Pennsylvania was found in a study to correlate with the average number of asthma cases in those cities. What type of study was this

Ecological study

Step-by-step explanation:

When the basis for the conclusion of a study is done an a group or population level rather than on a person, single or individual basis, then we refer to this as an ecological study. In the scenario described above, relationship between ozone in Pennsylvania and the number of asthma cases was generalized and presented on the mean or average level rather than being compared in terms of individual figure. Hence, research studies of this type or nature are classed as ecological study.