Suppose a 6-character password needs to be made using any of the letters A, X,Q, F,R, P and odd numbers between 0-10. How many passwords exist if: a) Any combination of these characters is allowed, and characters can be repeated. b) Repetition is not allowed. c) Alternate characters need to be letters or numbers, and repetition is not allowed.

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