When turning left, you must yield the right-of-way to
a. any vehicle behind you
b. vehicles to your right
c. any vehicles coming straight through from the other direction
d. pedestrians only

Dr. robbins wants to know if there are different opinions regarding the value of public school education between native americans who have at least one relative who attended indian boarding school and native americans who have no family experience with indian boarding school. dr. robbins contacts 35 native american participants in each group. he wants each group to include younger as well as older adults, and a mix of male and female participants. he asks each person to complete a survey about their attitudes toward public education. the design of this study is: