Define: voluntary responsea) every possible sample of a given size has the same chance to be selected. b) using extraneous factors to create similar groups. c) the explanatory variable(s) in an experiment. d) successively smaller groups are selected within the population in stages. e) people who choose themselves for a sample by responding to a general appeal. f) choosing the individuals easiest to reach. g) population is divided into similar groups and a srs is chosen from each group. h) gives each member of the population a known chance to be selected. i) directly holding extraneous factors constant.