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Homework Help: Density function

  1. Mar 9, 2010 #1
    p(t) = Ce-Ct

    i know P(t) is the fraction of the group surviving t years or less

    now the question is: suppose a patient has a 70% probability of surviving at least 2 years, find C.

    to find c i would take the integral of p(t) but what would my limits be? surviving 2 at least 2 years, so thats more than 2 years. would i have my lower limit be 2 and then have my upper limit be infiniti or just a big number?

    any help would be appreciated
     
  2. jcsd
  3. Mar 9, 2010 #2
    Not my field, but compute [tex]\int_0^xCe^{-Ct}dt[/tex]. What's the limit as x goes to infinity? Does it depend on C?

    I think you want to find C so that the integral from 0 to 2 years equals 70% of the integral from 0 to infinity.
     
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