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

Question

Quizplus · Accepted Answer

This was a controlled experiment because the researchers actively intervened by randomly assigning each carpet sample to a treatment group (vinegar, ammonia, or hydrogen peroxide) and then measured the outcome (the effectiveness of the stain removal). This direct manipulation of the independent variable (type of treatment) to observe its effect on the dependent variable (stain removal) is characteristic of an experimental design.

Use the Following Information for Following Questions