1. Introduction to Biology

What is the primary purpose of a control group in an experimental design?

Why is it important to include controls in an experiment?

The presence or absence of a vaccine in the experiment shown comprises the ______ variable.

In the study depicted in the figure above, why might researchers have measured blood pressure twice?

What is the purpose of the control group in an experimental design?

Should an experiment test only one variable at a time? Why or why not?

Which of the following options would allow Stella to set up a proper control group for her experiment?

The best method for determining whether bean plants require sodium is to __________.

In the context of experimental design, what is the purpose of a control group?

In the context of experimental design, what does 'replication' refer to, and why is it important?

In an experimental design, what is typically controlled in a controlled study?

In the context of experimental design, how many independent variables should a well-designed experiment test at one time?

What is the purpose of a control in an experiment?

Radon is a radioactive gas that seeps into homes from the soil. It is thought to be a cause of lung cancer. A research team investigates this hypothesis. The members of the team gather large amounts of data on basement radon concentrations and lung cancer rates and conclude that the more radon there is in a home, the more likely are people living in the home to develop lung cancer. After the study is published, other researchers criticize it by asserting that the studied neighborhoods with higher radon concentrations also have a higher percentage of older people and a higher percentage of cigarette smokers than the low-radon neighborhoods. Both advanced age and cigarette smoking increase the risk of lung cancer. This criticism, if correct, shows that the radon study suffered from __________.

Which of the following statements is true for an experimental study?