Identify the type of sampling bias guaranteed to occur in each of the sampling schemes, based on the information provided. Some sampling schemes have two types of bias.
A political poll is conducted by contacting people on landline phones.
A political poll is administered by contacting people on landline phones. The pollsters contacted 20000 households, and 4747 individuals agreed to speak with the caller.
A political poll is conducted by allowing users to register on a website and fill out an online survey.
A political poll asks the question, "If you found out that Candidate A was given a large sum of money by Special Interest Group B, would that change your opinion of how hypocritical Candidate A is?"
