Question

In: Math

Let X ∼ Pois(4), Y ∼ Pois(12), U ∼ Pois(3) be independent random variables. a) What...

Let X ∼ Pois(4), Y ∼ Pois(12), U ∼ Pois(3) be independent random variables.

  1. a) What is the exact sampling distribution of W = X + Y + U?

  2. b) Use R to simulate the sampling distribution of W and plot your results. Check that the simulated mean and standard error are close to the theoretical mean and standard error.

  3. c) Use the simulated sampling distribution to estimate P(W ≤ 14) and then check your estimate with an exact calculation.

Solutions

Expert Solution

please have a look at the R code

rx=rpois(500,4) #We have created 500 random observations from poisson distribution
ry=rpois(500,12)
ru=rpois(500,3)
rw=rx+ry+ru
plot(c(1:500),rw,type='p')
mean_w=mean(rw)
mean_w
sd_w=sqrt(var(rw))
sd_w
boolean_14=rw<=14 #It's a boolean vector giving TRUE if observation is less than 14
p=(sum(boolean_19))/500 #Sum(boolean_14) gives us number of rw observations which are less than 14
p
true_p=ppois(14,19) # It gives theoretical P(W<=14)
true_p

"Now have a look at the output"

simulated mean is coming out to be theoretical mean and simulated standard devaition (4.325) is very close to actual sd ( root(19)=4.3589). The simulated probabolity (0.146) is very close to actual probability (0.1497)


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