Final answer:
The use of random digit dialing in surveys exhibits selection bias due to the exclusion of non-telephone users, reliance on landlines, and potentially low response rates, all of which lead to an unrepresentative sample of the population.
The correct answer is C.
Step-by-step explanation:
When considering the source of bias in using random digit dialing to survey people about obstacles to exercising, selection bias is the potential issue. Not everyone has access to a telephone, and with the rise of cell phones, not all numbers are available in directories. People who are at home during the survey call, often landline users, are more likely to be older and possibly retired, making them unrepresentative of the general population. Additionally, a high number of cell phone users, particularly younger demographics, utilize cell phones exclusively, further contributing to the selection bias.
Furthermore, response rates can impact the reliability of a survey. As noted by the Pew Research Center, declining contact and cooperation rates in random digit dial surveys affect the validity of the findings, as does a low response rate, which leaves a survey vulnerable to sampling bias.
Another factor that can create a biased sample is omission of relevant data. If certain segments of the target sample, like working families, are consistently not home to respond to the survey, then the sample may lack essential perspectives needed for comprehensive data.