ABSTRACT
Before dealing with the various statistical tests, it is worthwhile deviating for a while to examine the nature of probability and how to calculate various probability values. Probability is described by a number which can range between 0 and 1. 0 indicates the absolute impossibility of the event concerned; 1 indicates absolute certainty; 0.5 indicates that there is an equal chance of the event occurring or not occurring. Similarly, probability can be described in percentages, that is 0 to 100%. The multiplication law of probability states that the probability of the joint occurrence of independent events is the product of the probabilities of the individual events. Sometimes it is necessary to know how many different ways things can be sorted in order. Permutations and combinations are used to calculate the number samples of a given size that can be chosen from a given population.
