What is required for sampling to be representative of the population?

For a sample to be truly representative of a population, it is essential that the sample is randomly selected. Random selection ensures that every member of the population has an equal chance of being included in the sample. This minimizes bias and increases the likelihood that the sample reflects the characteristics of the entire population. When the sample is selected randomly, it allows for a better approximation of the population's traits, which is crucial for making valid conclusions about the population based on the sample data.

In this context, the other choices do not fulfill the requirements for a representative sample. A smaller sample size may not capture the diversity and variability of the population adequately, while including all items from the population is typically impractical and not necessary for effective sampling. Excluding clearly irrelevant items can sometimes be justified, but it is not a fundamental requirement for ensuring that the sample is representative; the focus should be on the random selection process itself. Hence, the emphasis on random selection is pivotal for achieving representativeness in sampling.