A poll was published before a senate election predicting that Mrs. Jackson would win with 52 percent of the votes cast. Is this figure a sample statistic or a population characteristic?
To answer this question, let’s look at how we might define a sample statistic and a population characteristic. A population characteristic is a numerical summary of the entire population, that is, a numerical result obtained from data collected on every member of the population. A sample statistic, on the other hand, is a numerical summary of a sample. So a sample is taken from the population, and only data from that sample is used to produce a sample statistic.
To determine which of these two applies, let’s also define a poll. A poll, also called an opinion poll, is a survey of public opinion performed by questioning a representative sample of the population. Statistical results obtained from a poll are therefore, by definition, sample statistics. This means that our figure of 52 percent is a sample statistic.