simple random sample To determine if a candidate for state senator is popular with voters, 25% of voters in 160 counties are surveyed. stratified random sample To determine whether students think a new school library is needed, a computer generates a list of 100 random students and they are surveyed. systematic random sample To determine the freshness of doughnuts coming out of the oven, a baker selects a doughnut every 30 minutes and checks it.​