Let μ=E(X), σ=standard deviation of X. Find the probability P(μ-σ ≤ X ≤ μ+σ) if X has a Geometric distribution with p = 0.61. Round your answer to 4 decimal places.

Respuesta :

Answer:

P(μ-σ ≤ X ≤ μ+σ) = [tex]0.61 + 0.1275 = 0.7375[/tex]

Step-by-step explanation:

The geometric distribution is the number of failures expected before you get a success in a series of Bernoulli trials.

It has the following probability density formula:

[tex]f(x) = (1-p)^{x}p[/tex]

In which p is the probability of a success.

The mean of the geometric distribution is given by the following formula:

[tex]\mu = \frac{1-p}{p}[/tex]

The standard deviation of the geometric distribution is given by the following formula:

[tex]\sigma = \sqrt{\frac{1-p}{p^{2}}[/tex]

In this problem, we have that:

[tex]p = 0.61[/tex].

So

[tex]\mu = \frac{1-p}{p} = 0.6393[/tex]

[tex]\sigma = \sqrt{\frac{1-p}{p^{2}} = 1.0234[/tex]

P(μ-σ ≤ X ≤ μ+σ) = [tex]P(-0.3841 \leq X \leq 1.6627) = P(0 \leq X \leq 1.6627) = f(0) + f(1.6627)[/tex]

[tex]f(x) = (1-p)^{x}p[/tex]

[tex]f(0) = (0.39)^{0}(0.61) = 0.61[/tex]

[tex]f(1.6627) = (0.39)^{1.6627}(0.61) = 0.1275[/tex]

P(μ-σ ≤ X ≤ μ+σ) = [tex]0.61 + 0.1275 = 0.7375[/tex]