Key Idea To distinguish a quantitative variable from a categorical variable, we will use different symbols to refer to the statistics and parameters. In particular, Statistics x = sample mean s = sample standard deviation Parameters u = population mean " = population standard deviation Note that we are focusing on the mean and the standard deviation. (See Section 2.4 for more discussion about the median and Chapter 6 for discussion of another measure of variability.) 7. Identify the values of u and o for the length of words in the Gettysburg Address