Question

Prior to the mayoral election discussed in Exercise 33, the newspaper also conducted a poll. The paper surveyed a random sample of registered voters stratified by political party, age, sex, and area of residence. This poll predicted that Amabo would win the election with 52% of the vote. The newspaper was wrong: Amabo lost, getting only 46% of the vote. Do you think the newspaper’s faulty prediction is more likely to be a result of bias or sampling error? Explain. Choose correct answer and explain why:

Answer 1

The newspaper’s faulty prediction is most likely the result of sampling error. The description of the stratified sampling method does suggest that the sample is representative of the voting population. However, it is unclear whether the percentages by party, age, etc. were accurate when compared to the entire voting population. Random selection of individuals within each strata means that the sample statistics will vary from the population parameter. In addition, no measure of a sampling error percentage was given for the result.