Mutually Exclusive Events

• A mutually exclusive event is a probability that is always zero. This is because the probability cannot be produced since both variables cannot happen logically in reality. Mutually exclusive events are considered deterministic probabilities, meaning the probability will always happen. Only bizarre situations or the rules governing the variables being overturned can result in the probability not equaling zero. Certified Quality Engineers, a company that test preps engineers for certification exams, gives the probability example of a 25-year-old becoming President of the United States. This probability is impossible, since constitutionally, no 25-year-old can become the President of the United States.
  
  

Classical Events

• The classical approach is a method of probability assigned to see how often an event will happen. It is called the classical approach because it is seen as the central purpose of probability: calculating the likelihood of an event. Unlike a deterministic event, the classical approach tries to find the probabilistic outcome in a set. An example presented by Certified Quality Engineers is: how many games will there be in a sports championship series like baseball. Most championship series games have seven games at maximum. However, the team that wins the championship only needs to win four games. The mathematics department at the University of Illinois demonstrates this by stating that winning the first four games is a 1/8 probability, winning after five games is a 1/4 probability, and winning in the sixth or seventh game is a 5/16 probability.
  
  

Relative Frequency Events

• Relative frequency events are events that have a determined variable of time compared to what happened during that time. Relative frequency is deterministic in nature, since there is a finite number of variables being used. For example, a relative frequency event would be how many times a character says a catch phrase on a television program. The program's variable may be a season or the entire series of the program. Either way, there is only so many recorded times when the catch phrase is said. If there are 100 episodes and the catch phrase was said in 80 episodes, the probability is 80/100, or 4/5 of the time.
  
  

Subjective Events

• Subjective events are events in probability that contain random variables assigned by an individual. For example, if a meteorologist wants to inform the public on the likelihood of rain in the forecast, she must calculate variables she determines are important. There are endless variable sets to assign in a subjective event, since the person determines what is a valuable variable. The meteorologist might not think air pressure, for example, is a factor to include in a probability calculation, but another meteorologist might.