Many studies have demonstrated that high blood pressure increases the risk of stroke. A study suggested that a combination of high blood pressure and binge drinking could be lethal. The study followed 8200 men age 55 and over for three decades and found that men with high blood pressure who participated in binge drinking even occasionally had double the risk of dying from a stroke when compare to men with normal blood pressure who abstained from binge drinking.

Is this an observational study or experimental study?

The study is an experimental study because the researchers cannot control the response variable after three decades.

The study is an observational study because the researchers cannot control the response variable after three decades.

The study is an observational study because the researchers only observe values of the response and explanatory variables.

The study is an experimental because the researchers assign subjects to certain experimental conditions and observe the outcomes on the response variable.

Question 2:

Eighty mice that are susceptible to cancer are randomly divided into two groups. One group is treated daily with radiation similar to that generated by cell phones. The other group received no radiation. After one year, both groups are tested for cancer.

The response variable is:

Cell phone radiation

Group of mice

Cancer

Year

The explanatory variable is:

Cell phone radiation

Group of mice

Cancer

Year