Answer :
There are three highways in the county. the number of daily accidents that occur on these highways are poison random variables with respective parameters . 3, . 5, and . 7 The expected number of accidents that will happen on any of these highways today is 1.5
There is a theorem that we can use to find the expected value of a random variable that is a sum of other random variables as follows.
If X= X₁ + X₂ +...... +Xₓ, then E( X)= E(X₁) +E( X₂) +...... +E(Xₓ),
In this case, let X = the number of accidents that will happen on any of those highways today,
are the numbers of accidents on each highway, respectively.
Then X= X₁ + X₂ +X₃ .
Since are Poisson variates, their expected values are the parameters given, .3, .5 and .7.
So E(X₁) = .3 E( X₂) = .5 E(X₃)= .7
Thus, E(X)= 1.5
A similar Poisson random variable problem is given at
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