A local news agency conducted a survey about unemployment by randomly dialing phone numbers during the work day until it gathered responses from 1000 adults in its state. In the survey, 19% of those who responded said they were not currently employed. In reality, only 6% of the adults in the state were not currently employed at the time of the survey. Which of the following best explains the difference in the two percentages?

a. The difference is due to sampling variability. We shouldn’t expect the results of a random sample to match the truth about the population every time.

b. The difference is due to response bias. Adults who are employed are likely to lie and say that they are unemployed.

c. The difference is due to undercoverage bias. The survey included only adults and did not include teenagers who are eligible to work.

d. The difference is due to nonresponse bias. Adults who are employed are less likely to be available for the sample than adults who are unemployed.

e. The difference is due to voluntary response. Adults are able to volunteer as a member of the sample.

Select the best answer.