Final answer:
A sampling frame is a list or source that contains all the units eligible for selection in a sample. It is important in assuring the validity of a poll because it helps ensure that the sample represents the target population accurately and reduces the possibility of bias.
Step-by-step explanation:
A sampling frame is a list or source that contains all the units eligible for selection in a sample. It is important in assuring the validity of a poll because it helps ensure that the sample represents the target population accurately and reduces the possibility of bias. By using a sampling frame, pollsters have a defined population from which they can select their sample, making the results more reliable and generalizable.