Final answer:
Random sampling is a method where every element in the population has a nonzero chance of being included in a sample, and in the case of sampling without replacement, members once chosen are not returned before the next selection.
Step-by-step explanation:
When every element in a population has a nonzero probability of being included in a sample, this is referred to as random sampling. In random sampling, such as sampling without replacement, a member of the population may be chosen only once. With this method, after a member is selected, it is not returned to the population before the next draw, affecting the probabilities of subsequent draws. This approach ensures that all members have a chance to be included, resulting in a sample that aims to be representative of the entire population. Ensuring the sample is representative is crucial because, often, it is not practical to study an entire population due to its size.