PROBABILITY

Probability is determining the likelihood or odds that an event will occur. It is useful, therefore, for predicting outcomes of random trials. A subset of an outcome is an event, and it occurs when realized during a trial.

An occurrence of an event can happen when two or more events have no dependency on each other. Or an event can happen when two or more events are exclusive of each other. Regardless, the probability of an event can be calculated with or without prior observation. The sum of all probabilities must equal a value of one.

If no dependency exists between events, then the probability of their joint occurrences is the product of their individual probabilities. If a dependency exists, then the sum of their individual probabilities determines the probability of an occurrence of any event.

Probability calculations are useful for predicting outcomes. They are also useful for determining the accuracy of predictions.

for Calculating Probabilities

• Determine the objective of the calculations.
• Determine whether probabilities should be calculated prior to or after trials.
• Determine if the events are independent or exclusive of each other.
• Determine the appropriate sample size.
• Determine the appropriate probability distribution to calculate (e.g., normal distribution, binomial distribution).
• Calculate the probabilities.
• Conduct tests to verify the accuracy of the predicted probabilities.