Final answer:
Telephone surveys offer convenience but can suffer from self-selection bias. These surveys often use random-digit-dialing (RDD) for a representative sample, although call-in surveys might be classified as convenience sampling which is less reliable.
Step-by-step explanation:
Telephone surveys where people are asked to call in and provide responses can have several advantages and disadvantages. An advantage of such a survey is that it can be convenient for respondents since they can participate from their homes at a time that suits them. However, a significant disadvantage is the potential for self-selection bias, where individuals with strong opinions may be more likely to participate, skewing the results.
Sampling Technique in Telephone Surveys
The sampling technique used in phone-in surveys can vary. For scientific polling, organizations like Gallup may employ random-digit-dialing (RDD) to ensure a representative sample with a method that is more random than simply allowing respondents to call in. RDD helps in reaching a broader audience, including those with unlisted numbers or cell phones. However, with people self-selecting to call in, the survey might be more accurately described using convenience sampling, which is less scientific and may lead to results that cannot be generalized to the entire population.