Which of the following would decrease bias when selecting a sample for a controversial political survey? a. survey only registered voters b. conduct the survey on the internet c. advertise for participants on talk radio d. ensure that individual responses are confidential

The correct option is A.
In survey sampling, bias is defined as the tendency of the chosen sample to over estimate or under estimate  a population parameter. Bias is said to occur when the used sample does not accurately represent the population concerned; a good sample should be representative. There are different types of bias, depending on how they arise. When selecting a sample for controversial political survey, choosing participants from registered voters only will decrease the bias of the sampling.