Final answer:
The two most important elements in assuring that a public opinion poll sample is trustworthy are proper sampling techniques and random selection.
Step-by-step explanation:
The two most important elements in assuring that a public opinion poll sample is trustworthy are proper sampling techniques and random selection. By using probability sampling and randomly selecting samples from the larger population, researchers can ensure that everyone has an equal chance of being part of the sample. This allows for generalizations about the larger population and increases the accuracy of the poll.