Does Procellera Antimicrobial Wound Dressing help injuries heal faster? Researchers checked

records of 38 patients who has been treated for acute or chronic wounds between 2010 and 2012.

They found that those who had been treated with Procellera healed almost twice as fast.

(4 points)

a. Is this an observational study or an experiment?

b. If this is an observational study, which type is it - a cohort study or a case-control study?

c. What is the explanatory variable?

d. What is the response variable?