4. A study was conducted in New York City to determine which socioeconomic factors were associated with COVID-19.Below is the abstract from the study:

New York City was the first major urban center of the COVID-19 pandemic in the USA. Cases are clustered in the city, with certain neighborhoods experiencing more cases than others. We investigate whether potential socioeconomic factors can explain between-neighborhood variation in the COVID-19 test positivity rate.

Data were collected from 177 Zip Code Tabulation Areas (ZCTA) in New York City (99.9% of the population). We used the positivity COVID-19 rate in each zip code as the outcome, a set of 11 representative demographic, economic, and health-care associated ZCTA-level parameters as potential predictors, and the total number of COVID-19 tests as the exposure.

a.What type of study design was used?