Why use sampling?


The most precise description of a population comes from accurate measurements of each member of the population, which is a census. However, a census is typically impossible because of cost and logistical problems. Imagine trying to measure every tree in a 1-million hectare forest. A sample measures a portion of the population, and in forestry, this is usually a very small portion. Estimates derived from data collected from the measured sample is then extrapolated to the entire population, most of which has not been measured. Think of this as ¿guessing¿ or ¿estimating¿ the condition of a population based on sampling a few members of that population. If the sample is representative of the entire population, then the estimate will be accurate and unbiased. Otherwise, estimates will be inaccurate and misleading; it will not be apparent that the estimates are inaccurate; and the accuracy of estimate will not be known because the true condition of the whole population will not be known. The