For example, if we wished to conduct a national inventory to determine the volume of commercially valuable timber in a National Forest, the population would comprise all trees of a harvestable size within that National Forest. In another situation, a Bureau of Land Management field officer may want to know the biomass of forage within a particular pasture, to determine its stocking rate over the next 12 months. This time, the population is confined to the forage species within that pasture, excluding the unpalatable or inaccessible material that will not be consumed.
Because it is usually impractical or impossible to measure all members of the population, a sample is selected and measured to obtain information on the population.
References and Further Reading
Cochran, W.G. 1977. Sampling techniques. John Wiley Sons, New York, NY.
Dowdy, S. and S. Weardon. 1991. Statistics for research. John Wiley Sons, New York, NY. 2nd ed. pp 21-22.