Each bag of Skittles is supposed to have at least 30 Skittles. A machine that fills bags has a 0.005 probability of under filling a bag. For every thousand bags, what is the standard deviation for the number of bags (out of a thousand) that are under-filled. Assume the Poisson distribution.

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Answer:

The standard deviation for the number of bags that are underfilled is 2.236.

Step-by-step explanation:

In a Poisson distribution, the probability that X represents the number of successes of a random variable is given by the following formula:

[tex]P(X = x) = \frac{e^{-\mu}*\mu^{x}}{(x)!}[/tex]

In which

x is the number of sucesses

e = 2.71828 is the Euler number

[tex]\mu[/tex] is the mean in the given interval. The variance is the same as the mean, which mean that the standard deviation is the square root of the mean.

In this question:

Expected number of underfilled bags in a sample of n bags is:

[tex]\mu = 0.005*n[/tex]

1000 bags, so

[tex]\mu = 0.005*1000 = 5[/tex]

Standard deviation [tex]S = \sqrt{5} = 2.236[/tex]

The standard deviation for the number of bags that are underfilled is 2.236.