The subjective probability is one that is based on individual experience. The person evaluates the possibilities and assigns the values according to the previous facts that you know.

It is possible to link the subjective probability to a relative frequency or to a guess. The subject measures the degree of probability according to the verisimilitude which gives every possible outcome.


Subjective probability is not based on certainties, but on previous experiences.

Lack of certainties

Recall that, in a random experiment, it cannot be established with certainty whether or not a certain event will happen in a specific trial. When measuring the probability the event in question can be assigned a number.

In the case of subjective probability, the estimation of the occurrence of the event is based on the intuition or in the opinion, generally derived from previous experiences. The individual analyzes the information that arranges and gives a probability value to the event according to their level of belief about the event actually occurring.


When a person who is not an expert in meteorology anticipates that it will rain, he resorts to subjective probability.

Weather forecast and subjective probability

It is common for someone to resort to subjective probability when referring to forecast of weather. Those who are not a meteorologist or have the ability to interpret scientific information from satellites can rely on their own experience to estimate how likely it is that it will rain in the next few hours. If express “I think there is a 90% chance that it will start to rain before sunset.”, you will be appealing to subjective probability.

The subjective probability, in short, is a way of quantifying the probability of occurrence of an event from individual factors from weighing. This resource can be useful when there is no other way to quantify that is more reliable.