In research, sampling is the part where we collect the information that can be later analyzed by various methods. The aim of sampling is to collect physical evidence (such as water samples, other fluids, rocks, soil, etc.) and or verbal responses (in surveys). Research is extrapolated to have significance in a much larger population, however it is impractical to collect information from an entire population. Sampling allows researchers to collect data from a few selected items (called samples, and hence the process of sampling) instead of the entire population and then project the results. Sampling can be random (picking samples at random from a mostly homogeneous population) or stratified (random sampling from within each strata of the population, say based on age or educational level, etc.) or sequential (conducted at sequential intervals).
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