The article explores how a group of people feel about a new policy by surveying 100 random members. Since the true population variance is unknown, the sample variance is used instead to calculate a 95% confidence interval. Using the sample variance introduces more uncertainty. The hypothesis is that the true population mean could be 4.0. The standard error of a sample mean is estimated using the sample variance and sample size. This estimate accounts for the uncertainty introduced by using the sample variance instead of the population variance.