A researcher has hypothesized that the chemical tributyltin (an additive in boat paint)seeps out of the paint into the water and causes reproductive defects in developing marine snails. Which of the following would be a good control in an experiment that tests the effects of tributyltin on developing snails?
A) Developing snails are kept in a tank of water and exposed to below-expected levels of tributyltin.
B) Developing snails are kept in a tank of water and exposed to boat paint that does not contain tributyltin.
C) Developing snails are kept in a dry tank to avoid exposure to contaminated water.
D) Developing snails are kept in a tank of water that has never been exposed to boat paint.

Question

Quizplus · Accepted Answer

A good control in this experiment would involve exposing developing snails to a substance very similar to tributyltin, but without the actual additive. Option B specifies exposing the snails to boat paint without tributyltin, which is a good control. Option A only exposes the snails to below-expected levels of tributyltin, which could still have an effect, and option C avoids exposure to the variable altogether. Option D does not address the variable of interest, tributyltin.

A Researcher Has Hypothesized That the Chemical Tributyltin (An Additive