In an experimental study, researchers are testing a new flea preventive medication on dogs using a blind study. Dogs are treated with the new medication or with a placebo. Who should know which dogs are given the medication or the placebo for this blind study?

If all parties involved know which dogs receive the medication or placebo, it introduces bias that can affect both the treatment administration and the interpretation of results. This knowledge could inadvertently influence how the researchers monitor the dogs' responses or how the owners report observations.

Allowing only the dog owners to know the treatment assignment would compromise the study's blind design. Their awareness could lead to biased reporting of outcomes, as owners may have preconceived notions of how their dogs should behave based on the treatment they believe their dog received.

While it is important for researchers to maintain control over the experiment, having them know which dogs receive the treatment would violate the principles of a blind study. Their knowledge could unconsciously influence their behavior or data collection methods, ultimately affecting the validity of the findings.