Tony bought 3 boxed of 1 inch nails for a total of 252 1 inch nails and 5 boxes of 2 inch nails that had equal amounts of nails. he bought a total of 507 nails. find the number of nails in each box of 2 inch nails.

Researchers are conducting experiments to determine the role of alcohol in the development of depression. after the study is complete, they determine that the relative risk of developing depression is 1.55 with a 95 % ci of 1.2 -1.9. each group is then divided into nonsmokers and smokers. the relative risk for the nonsmokers is 1.12 with a 95% ci of 0.87-1.37. the relative risk for the smokers is 1.7 with a 95 % cl of 1.5-1.9. what type of bias may affect this study? a. procedure bias b. recall bias c. selection bias d. confounding e. lead-time bias