ABSTRACT
As we stated in Chapter 3, a population is defined as the entire collection of measurements about which we want to make a statement, such as all possible measurements of dissolved oxygen in a specific section of a stream within a certain time period. Probability distributions are idealized mathematical models that are used to model the variability inherent in a population (e.g., all measures of dissolved oxygen will not exactly match each other). Certain probability distributions come up again and again in environmental statistics. This chapter discusses the concepts of a random variable and a probability distribution, talks about important probability distributions in environmental statistics, and shows you how to use various functions in S-PLUS and ENVIRONMENTALSTATS for S-PLUS to plot and generate quantities associated with probability distributions.
