Estimating a Population Proportion
If there is interest in the composition of a population, we could use a simple random sample to estimate the proportion of the population p that is composed of elements with a particular trait, such as the proportion of plants that flower in a given year, the proportion of juvenile animals captured, the proportion of females in estrus, and so on. We will consider only classifications that follow binomial trials which means that either an element in the population has the trait of interest (flowering) or not (not flowering) although extending this idea to more complex settings is straightforward. In the case of simple random sampling, the population proportion follows the mean exactly; that is, p = μ. If this idea is new to you, convince yourself by working through an example. Say we generate a sample of 10 elements, where 4 have a value of 1 and 6 have a value of 0 (1 = presence of a trait, 0 = absence of a trait). The proportion of the sample with the trait is 4/10 or 0.40 and so is the arithmetic mean, which = 0.40 ([1+1+1+1+0+0+0+0+0+0]/10 = 4/10). Cosmic. It follows that the population proportion (p) is estimated with the sample proportion ( p ˆ ) which has an unbiased estimator:
มีประชากรประมาณ สัดส่วนIf there is interest in the composition of a population, we could use a simple random sample to estimate the proportion of the population p that is composed of elements with a particular trait, such as the proportion of plants that flower in a given year, the proportion of juvenile animals captured, the proportion of females in estrus, and so on. We will consider only classifications that follow binomial trials which means that either an element in the population has the trait of interest (flowering) or not (not flowering) although extending this idea to more complex settings is straightforward. In the case of simple rando m sampling, the population proportion follows the mean exactly; that is, p = μ. If this idea is new to you, convince yourself by working through an example. Say we generate a sample of 10 elements, where 4 have a value of 1 and 6 have a value of 0 (1 = presence of a trait, 0 = absence of a trait). The proportion of the sample with the trait is 4/10 or 0.40 and so is the arithmetic mean, which = 0.40 ([1+1+1+1+0+0+0+0+0+0]/10 = 4/10). Cosmic. It follows that the population proportion (p) is estimated with the sample proportion ( p ˆ ) which has an unbiased estimator:
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