Final answer:
True random sampling is important for external validity, but practical constraints often lead researchers to use convenience samples that may not be fully representative of the whole population. Findings from these samples should be interpreted with caution.
Step-by-step explanation:
The question relates to the process of random sampling which has implications for the external validity of a study's results. True random samples are ideal as they represent the whole population and allow for accurate inferences to be made about public opinion or other study topics. However, obtaining a random sample can be challenging due to practical constraints. As a result, researchers often resort to using a convenience sample, which is easier and more economical but may not be as representative of the whole population.
For example, selecting participants from Introduction to Psychology courses may skew results as it does not account for the full diversity of the entire population. Although this method is less representative, convenience sampling has the benefit of being more feasible in some research situations. It is crucial to note that findings from such samples should be cautiously interpreted since its generalizability may be limited.