Understanding the Difference Between Possibility and Probability

When it comes to expressing likelihood or certainty about events, two terms often used interchangeably are possibility and probability. These terms, although related, have distinct meanings in terms of how they quantify and communicate the likelihood of an event occurring.

Possibility

Definition: Refers to something that can happen or be true, regardless of how likely it is. It indicates that there is a chance, however small, for an event to occur.

Example: In April, it is possibly cold outside, meaning that while it might be cold, it could also be warm. This term is used to denote the potential existence of an outcome without guaranteeing it.

Probability

Definition: Refers to the likelihood or chance that a particular event will occur. It is often measured on a scale from 0 to 1 or 0 to 100, indicating how likely something is to happen.

Example: In January, it is probably cold outside, meaning that the likelihood of it being cold is significantly higher than the possibility of it being warm. This term is used to quantify the likelihood of an event occurring.

Summary: Possibility implies that something can happen but does not indicate how likely it is; while Probability provides a measure of how likely something is to happen.

Usage of Possibly vs. Probably

The distinction between these terms becomes evident in how they are used to express likelihood in specific contexts.

Possibly: The term "possibly" is used to acknowledge that an event can occur, but it comes with a qualifier of extremely unlikely. For example, a chess grandmaster might possibly be checkedmate in seven moves, but it would be an extremely unlikely outcome.

Probably: The term "probably" is used to indicate a higher likelihood of an event occurring. It suggests that the outcome is more likely to be the case than not. For example, in a coin toss, while you might possibly get three heads in a row, the probability of this happening is very low.

Etymology and Usage

The word "probable" comes from the same root as "provable," indicating that while everything that is probable might not be provable, the concept of a particular outcome being somewhat predictable is crucial in understanding the difference between "possibly" and "probably."

Here are some numerical examples to further illustrate the difference:

50.1% is probable, indicating a significant likelihood of an outcome. 0.000001% is possible, indicating an extremely unlikely outcome.

For example, in three tosses of a coin, getting two heads and one tail is probably the outcome, as it is a more likely sequence than getting all heads or all tails. However, getting three heads or three tails is possible, but not probable.

Conclusion

Understanding the difference between possibility and probability is essential for clear communication. While possibility acknowledges the potential for an event, it does not quantify the likelihood. On the other hand, probability offers a measure of how likely an event is to occur, making it a crucial tool in decision-making and risk assessment.