Use the Following Information for Following Questions

Multiple Choice

Use the following information for following questions:. Which treatment is most effective at
treating carpet stains: vinegar, ammonia, or hydrogen peroxide? In a study, researchers randomly assigned
55 carpet samples with identical stains to one of three groups. Depending on which group they were
assigned to, each carpet sample received a home remedy of water mixed with vinegar, ammonia, or
hydrogen peroxide. Afterwards, each carpet sample was examined and any remaining stain was measured.
Researchers found that a vinegar and water mixture produced better results than both ammonia and
hydrogen peroxide.
-Was this a controlled experiment or an observational study?

A) Experimental because researchers determined, through randomized assignment, which treatment each carpet sample received
B) Experimental because researchers could not determine how much of the stain was removed
C) Observational study because researchers determined which treatment each carpet sample received
D) Observational study because the carpet samples were not a random sample