Probability refers to the chance that an event will occur. To calculate probability of the outcome we need to take number of occurrences and divide it by total number of possible outcomes.The lowest probability is 0 and the highest is 1.
Probability = number of occurrences / total number of possible outcomes
For example, we can take number of household fires over certain period in a certain area and divide it by total number of households in the same area. This will give us a probability of fire in the households in this particular area.