Questions: 1) One study of cell phones and the risk of brain cancer looked at a group of 469 people who have brain cancer. The investigators matched each cancer patient with a person of the same age, sex, and race who did not have brain cancer, then asked about the use of cell phones. Result: "our data suggest that the use of hand-held cellular phones is not associated with risk of brain cancer. a) Is this an observational study or an experiment? Justify your answer. b) Based on this study would you conclude that cell phones do not increase the risk of brain cancer? Why or Why not?

1. One study of cell phones and the risk of brain cancer looked at a group of 469 people who have brain cancer. The investigators matched each cancer patient with a person of the same age, sex, and race who did not have brain cancer, then asked about the use of cell phones. Result: "our data suggest that the use of hand-held cellular phones is not associated with risk of brain cancer."

a) Is this an observational study or an experiment? Justify your answer.

The answer is: This is an observational study.

Explanation:

• In an observational study, researchers observe and collect data without manipulating the study environment or the subjects. They do not assign treatments or interventions to the subjects.
• In this case, the investigators did not assign cell phone usage to the participants. Instead, they observed and recorded the cell phone usage habits of people who already had brain cancer and compared them to those who did not have brain cancer.
• The matching of cancer patients with non-cancer individuals based on age, sex, and race is a method to control for confounding variables, but it does not change the nature of the study from observational to experimental.

b) Based on this study would you conclude that cell phones do not increase the risk of brain cancer? Why or Why not?

The answer is: No, you should not conclusively conclude that cell phones do not increase the risk of brain cancer based on this study alone.

Explanation:

• While the study suggests that there is no association between cell phone use and brain cancer, observational studies have limitations that prevent definitive conclusions about causality.
• Observational studies can be affected by confounding variables that were not controlled for, which might influence the results.
• The study's design only shows correlation, not causation. It cannot definitively prove that cell phone use does not cause brain cancer.
• Further research, including well-designed experimental studies (such as randomized controlled trials), would be needed to establish a causal relationship or lack thereof.
• Additionally, the sample size and the specific population studied (469 pairs) may not be representative of the general population, and other factors such as duration and frequency of cell phone use were not detailed in the question.