10.1 Two population means with unknown standard deviations  (Page 24/24)

a characteristic of interest in a population being studied. Common notation for variables are upper-case Latin letters X , Y , Z ,... Common notation for a specific value from the domain (set of all possible values of a variable) are lower-case Latin letters x , y , z ,.... For example, if X is the number of children in a family, then x represents a specific integer 0, 1, 2, 3, .... Variables in statistics differ from variables in intermediate algebra in two following ways. The domain of the random variable (RV) is not necessarily a numerical set; the domain may be expressed in words; for example, if X = hair color, then the domain is {black, blond, gray, green, orange}. We can tell what specific value x of the random variable X takes only after performing the experiment.