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Scouting Citrus for Pests - Page 5
Dealing with Sampling Error
The objective of scouting is to obtain an estimate of true pest incidence based on a representative sample. Given that the number of fruit or leaves that we might inspect is only a tiny fraction of the total, there is ample room for error, of which basically, there are two types. Random error is due to natural variation, and should be distributed evenly around the mean or average which it masks. The more the population is aggregated or clumped, the greater will be the random error. The only way to reduce random error is to increase sample size. Error which is consistent and tends in a certain direction is called bias. It is caused by sampling in a particular way that favors one part of the population over another. Examples might be sampling
certain rows, sides of the tree, size fruit, etc. Bias can be avoided with a sampling plan that employs randomization at some, if not all levels.
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