Final answer:
Using a sample of a population is helpful when the population is large, and conducting a full survey would be too time-consuming or expensive. Random sampling ensures equal representation and provides a practical method for data collection.
Step-by-step explanation:
It is often helpful to use a sample of a population in situations where the population is very large, such as in the case of national surveys or product quality checks for a massive batch. Moreover, sampling is practical when it would take a lot of time, require considerable resources, or cost a significant amount of money to survey the entire population. In terms of research effectiveness, using a random sample is particularly efficient because every individual in the population has an equal chance of being selected, which helps to ensure that the sample is representative of the entire population. Therefore, selecting a random sample is an effective way to gather data that could provide insights into the entire population without the impracticalities of engaging with every individual.