Question: A scientist was hired to determine which brand of toothpaste is more effective in preventing cavities in children. Thirty children volunteered to participate in the experiment from which the scientist randomly created two groups of 15 children. The first group was given Brand A toothpaste, and the second group was given Brand B toothpaste. All of the children were given detailed directions describing when and how they should brush their teeth. After six months the children were taken to the same dentist and the number of cavities each child had was recorded. This data was used to determine which toothpaste is more effective.

A. Identify something the scientist tried to control in this experiment. Identify something the scientist did not consider controlling or was unable to control in this experiment and explain the adverse effects this might have had on the collected data.

B. Explain how replication was used in this experiment and why it is important.

C. The scientist randomly created the two groups. Instead, the scientist could have created the two groups based on some common characteristic, such as age or gender. Explain the adverse effects this might have had on this experiment.

D. Explain the role comparison plays in experiments and specify what was compared in this experiment.