Chapter 4: Deriving Poisson Process

Discussion in 'CT3' started by vidhya36, Sep 1, 2014.

  1. vidhya36

    vidhya36 Very Active Member

    Can someone explain the condition (ii) of Poisson process?

    P(N(t + h) = r | N(t) = r ) = 1- lambda h + o(h)
    P(N(t + h) = r + 1|N(t) = r ) = lambda h + o(h)
    P(N(t + h) > r + 1|N(t) = r ) = o(h)
    (Note that a function f (h) is described as o(h) if lim h-->0 [f(h)/h] = 0)

    How this came? And how to deduce this: "Condition (ii) states that in a very short time interval of length h, the only possible numbers of events are zero or one. Note that condition (ii) also implies that the number of events in a time interval of length h does not depend on when that time interval starts."
     
  2. Hemant Rupani

    Hemant Rupani Senior Member

    As \(\lamda \) is a mean for a time..... Therefore for small time interval h mean is \(\lamdah \)
    Now for first part Probability of occurring zero is \(e^{-\lamdah}=1- \lamdah + o(h) \)
    And for second Probability of occurring one is \(\lamdah*e^{-\lamdah}= \lamdah + o(h) \)
     
  3. vidhya36

    vidhya36 Very Active Member

    Okay. Got it.
     

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