Final answer:
The sampling method used in the 1965 research was random digit dialing, a type of probability sampling. Potential biases could arise from the fact that not everyone has a telephone, and the sample may miss people not at home.
Step-by-step explanation:
In 1965, researchers conducted a survey by using random digit dialing (RDD) to call 1300 people and inquire about their non-attendance at town hall meetings. This method is a form of probability sampling, where each member of the population has an equal chance of being selected. However, there are potential sources of bias. Not everyone owns a telephone, and the timing of the calls may result in missing certain demographics who are not home. Additionally, the sharp decline in landline use and rise in mobile phones can introduce biases, as mobile phone numbers may not be listed and are often carried throughout the day, possibly excluding those who are not at home during typical calling hours.
Selection bias is a key concern with random digit dialing, as those who only use cell phones or have unlisted numbers might be underrepresented. Moreover, the shift in phone usage patterns can cause a bias toward older individuals and those more likely to be at home. To mitigate these issues, pollsters may ask for ZIP codes and other demographic information early in the survey to adjust the sample and ensure it remains representative of the target population. Modern polling techniques often combine telephone-based RDD with Internet-based surveys and automated interviewing systems to broaden their reach and improve accuracy.