The Student Room Group
Reply 1
alwaysingtogeth
A normal person has a mean of 3 parts per million of something in their body exponential distribution. What is probabilty a perso exceeds 8 parts per million??


For exponential distributions, E[X]=1/(lambda), where lambda is the distribution parameter. Hence, E[X]=3=1/L --> L=1/3, so that the distribution is defined by f(x)=(e-x/3)/3. P{X>8}=1-P{X<=8}=1-Int(0 to 8)f(x)=1-(-e^-(8/3)+1)=e^-(8/3)=0.069