ie total area under graph = certancy = 1

ie probability of x being between a and b

= Expected value of x = ( average)

= Varience of x = ( standard deviation)

## Normal Distribution

`Often applies where sample size is
large.
`

`0.3 Probability density = P(x)`

`=
`

`0.2
`

`0.1
`

## PoissonDistribution

`probability of r events in time t`

`= average no of `

`events in time t`

`mean = `

`varience =
`

## Exponential Distribution

`E(x) = `

`V(x) =
`