A case-control study was conducted to assess the relationship between cell phone use and brain tumors. Cases were men and women, age 24 to 40, who had been diagnosed with a brain tumor during the six months prior to study recruitment. A group of men and women who had never been diagnosed with brain tumors were selected as controls. Cell phone use was measured as high use and low use.
Cases Controls Total
High cell phone use 201 109 310
Low cell phone use 116 344 460
Total 317 453 770
a. What is the appopriate risk estimate to calculate for this study: ________________
