Probability Values

Understanding Probability Values

• Probability values quantify the likelihood of an event occurring.
• A probability value ranges from 0 (impossible event) to 1 (certain event) under ideal circumstances.
• A probability value of 0 means the event is certain not to happen.
• A probability value of 1 means the event is certain to happen.
• A probability value of 0.5 means the event is as likely to happen as it is not.
• The closer the probability is to 1, the more likely the event is. The closer to 0, the less likely it is.

Working with Probability Values

• Probability values can be added together if the events are mutually exclusive (cannot both occur at the same time).
• However, probabilities cannot exceed 1. If the total exceeds 1, there is an error in the computation or the events are not actually mutually exclusive.
• When events are independent (occurrence of one does not affect the other), their probabilities are multiplied to find the joint probability.

Probability Values and Outcomes

• If all outcomes are equally likely, the probability of each outcome is 1 divided by the number of outcomes.
• The sum of the probabilities of all possible outcomes is always equal to 1.
• An unlikely event has a probability value close to 0, while a likely event has a value close to 1.

Probability Values and Frequency

• Probability can also be understood as a long-term frequency of happening.
• If a coin is tossed many times, the proportion of heads gets closer and closer to 0.5, this is called the law of large numbers.