Types of distribution

Types of distribution

1. Exponential distribution

   • Definition
     • While the distribution of Poisson describes the arrivals per unit of time, the exponential distribution studies the time between each of these arrivals. If the arrivals are from Poisson the time between these arrivals is exponential. While the distribution of Poisson is discreet the exponential distribution is continuous because the time between arrivals does not have to be an integer.
   • Usage
     • This distribution is widely used to describe the time between events. More specifically the random variable that represents the time needed to serve the arrival.

2. Weibull

   • Definition
     • In probability theory and statistics, the Weibull distribution is a continuous probability distribution. It is named after Swedish mathematician Waloddi Weibull, who described it in detail in 1951, although it was first identified by Fréchet (1927) and first applied by Rosin & Rammler (1933) to describe a particle size distribution.
   • Usage
     • In hydrology the Weibull distribution is applied to extreme events such as annual maximum one-day rainfalls and river discharges.
     • In forecasting technological change (also known as the Sharif-Islam model)
     • In reliability engineering and failure analysis

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