Final answer:
The sampling technique used in the 1965 research was random digit dialing, a type of probability sampling. Potential sources of bias include lack of telephone ownership, unlisted cell phone numbers, and absence during call times. Researchers can mitigate these biases by including demographic questions early in surveys and adopting contemporary methods like Internet-based surveys.
Step-by-step explanation:
The type of sampling used in the 1965 research on obstacles to eating healthier was random digit dialing, a technique related to probability sampling. This approach randomly selects individuals from a larger population, ensuring that everyone has an equal chance of being included in the sample.
However, potential sources of bias in this method include the possibility that not every individual has access to a telephone, the fact that cell phone numbers may not be listed, and the increased likelihood that people may not be home to answer calls.
Additionally, since 2020, many people have transitioned to using cell phones exclusively, which can skew samples drawn from landlines to older demographics or individuals who are frequently at home.
To avoid such biases and increase the accuracy of polling, researchers may include questions about ZIP codes or demographics early on to determine the representativeness of the respondent.
However, efforts to create a representative sample are challenged by factors such as declining contact rates in telephone surveys and changing communication habits. The use of Internet-based surveys and automated interviewing systems is becoming more common as researchers seek methods that reflect current trends.