Previous sessions focused on the analysis of variation in data and the possible sources of the variation. A new source of variation is considered in this session -- randomness. The description of variation due to randomness depends on the ideas of mathematical probability.
This session does not attempt to give a formal definition of probability, nor of such concepts as sample space or random variables, though these ideas are explored. The binomial model is developed from tree diagrams only for an equally likely case (tossing a "fair" coin) and cases where the number of trials ("tosses") is four or less. Counting rules are not used.
Ultimately, an informal treatment of a "goodness of fit" problem is investigated to show how a probability model might be used in the analysis of a statistical problem.