Using a Sample to Estimate Characteristics of One Population

In this section the theory developed in Part III is used to allow us to infer the characteristics of a population based on data from a sample. This is an essential part of statistical analysis because we often need to know about the parent population, but are not able to study every one of its members. For example, we might like to know what percentage of voters favor a particular political issue, but cannot survey all voters by phone; or we may need to know if a particular medication is effective, but cannot wait (or afford) to test it on every individual who contracts the disease before declaring it as effective or ineffective.