Random sampling means that every sample drawn from a population has an equal probability of being chosen.
Use: Random sampling is important because when drawing from the population, one wants to have no bias in the sample drawn. For example, if samples are taken from only the top of the pile in a batch, those pieces that are on top were probably all made at a point in time that was much later than those parts that are on the bottom of the barrel. If something changed in the process that is time related, and if only the parts chosen as samples are taken from the top of the pile, the variation due to time would not be detected. In many cases, random number generators are used to eliminate bias when drawing samples.
