10.1 Hypothesis testing: two population means and two population  (Page 5/5)

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.