If a researcher manipulates one of the variables in a study and tries to determine how the manipulation influences other variables, the researcher is conducting a(n) (a) manipulative study observational study ( b ) (e) none of the above independent study experimental study What type of sampling is being employed if I survey the students at a college by randomly selecting a number of classes and survey everyone in each of those classes? (a) cluster (c) random (e) convenience ( b ) stratified (d) systematic