This Demonstration illustrates some descriptive statistics and two different types of statistical estimation: a confidence interval for the mean of the underlying population (the validity of which depends on the normality of the underlying population) and a statistical test of the hypothesis that the population is not normally distributed. You can change the segment of the population that forms the sample and see the change in sample characteristics (mean, median, and so on). Use the sliders to set the bounds of the sample and to set the sample size and type.