We saw the idea of population summaries illustrated with the birth-weight data in Chapter 3, where we called the sample mean a statistic, and the population mean a parameter. In more technical statistical writing, these two figures are generally distinguished by giving them Roman and Greek letters respectively, in a possibly doomed attempt to avoid confusion; for example m often represents a sample mean, while the Greek μ (mu) is a population mean, and s generally represents a sample standard deviation, σ (sigma) a population standard deviation.
