A group of epidemiologists decides to study the possible relationship between the use of cell phones (exposure) and the occurrence of brain tumors (disease). They identify a sample of adults, representative of an urban community. The sample has a total of 10,000 individuals. They identify 9,000 individuals who use cell phones and 1,000 individuals who do not use them. The proportion of men and women, as well as the age distribution of both groups, is similar. After observing these 10,000 individuals over a period of thirteen years, the researchers found 18 subjects who were diagnosed with brain tumors among cell phone users. Among the NON cell phone users, there was 1 individual who developed a brain tumor during the study period.

1. Fill in the spaces of the 2x2 table (contingency) with the data obtained from the study:

	Brain tumor	No brain tumor	TOTAL
Yes cell phone
Not cell phone
TOTAL

2. What is the design of this study? ________________________

3. The relative risk (RR) of acquiring a brain tumor from cell phone exposure, based on the results of this study, is ____________. Perform the calculation.

4. The percentage (proportion) of brain tumors in those exposed that can be attributed to cell phone use is = ______%. Perform the calculation.

5. The percentage (proportion) of brain tumors in the population that can be attributed to cell phone use is = ____%.