Ms. Alvarez wants to determine the seventh graders’ preferences for the location of the end-of-year field trip. Which of the samples is representative of the population?
A- All students in Ms. Alvarez's fifth-period class
B- All students in Ms. Alvarez's advisory group
C- Every third student from an alphabetical list of all students in the entire school district
D- Every fifth student from an alphabetical list of all seventh graders in the school

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