This is a Statistics problem.  Is the sample mean from the Poisson distribution normally distributed?

MATLAB: An Introduction with Applications
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This is a Statistics problem. 

Is the sample mean from the Poisson distribution normally distributed? 

Example 5.21
Let X1,..., X30 be independent Poisson random variables with rate 2. From our knowledge of the
Poisson distribution, each X, has mean u = 2 and standard deviation o = v2. Assuming n = 30 is
a large enough sample size, the Central Limit Theorem says that
X – 2
Z =
V2/V30
will be approximately normal with mean 0 and standard deviation 1. Let us check this with a
simulation.
This is a little bit more complicated than our previous examples, but the idea is still the same. We
create an experiment which computes X and then transforms it by subtracting 2 and dividing by
V2/V30.
Here is a single experiment:
Xbar <- mean (rpois (30, 2))
(Xbar - 2) / (sgrt(2) / sgrt(30))
## [1] 0.1290994
Now, we replicate and plot:
z <- replicate(10000, {
Xbar <- mean ( rpois (30, 2))
(Xbar - 2) / (sqrt (2) / sqrt(30))
})
plot(density(Z),
main = "Standardized sum of 30 Poisson rvs", xlab = "Z"
curve(dnorm(x), add = TRUE, col = "red")
Standardized sum of 30 Poisson rvs
Figure 5.4: Standardized sum of 30 Poisson random variables compared to a standard normal rv.
In Figure 5.4 we see very close agreement between the simulated density of Z and the standard
normal density curve.
Density
0.0 0.1 0.2 0.3 0.4
TIT
Transcribed Image Text:Example 5.21 Let X1,..., X30 be independent Poisson random variables with rate 2. From our knowledge of the Poisson distribution, each X, has mean u = 2 and standard deviation o = v2. Assuming n = 30 is a large enough sample size, the Central Limit Theorem says that X – 2 Z = V2/V30 will be approximately normal with mean 0 and standard deviation 1. Let us check this with a simulation. This is a little bit more complicated than our previous examples, but the idea is still the same. We create an experiment which computes X and then transforms it by subtracting 2 and dividing by V2/V30. Here is a single experiment: Xbar <- mean (rpois (30, 2)) (Xbar - 2) / (sgrt(2) / sgrt(30)) ## [1] 0.1290994 Now, we replicate and plot: z <- replicate(10000, { Xbar <- mean ( rpois (30, 2)) (Xbar - 2) / (sqrt (2) / sqrt(30)) }) plot(density(Z), main = "Standardized sum of 30 Poisson rvs", xlab = "Z" curve(dnorm(x), add = TRUE, col = "red") Standardized sum of 30 Poisson rvs Figure 5.4: Standardized sum of 30 Poisson random variables compared to a standard normal rv. In Figure 5.4 we see very close agreement between the simulated density of Z and the standard normal density curve. Density 0.0 0.1 0.2 0.3 0.4 TIT
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