Question

Suppose the number of messages that an inbox receives may be modeled by a Poisson distribution. If the average number of messages per hour is 18, then what is the probability it will receive between 15 and 20 messages during any given hour?

Answer 1

Answer:

0.36427

Step-by-step explanation:

Mean = λ = 18 messages per hour

P(X = x) = (e^-λ)(λ⁻ˣ)/x!

P(X ≤ x) = Σ (e^-λ)(λ⁻ˣ)/x! (Summation From 0 to x)

But the probability required is that the messages thay come in an hour is between 15 and 20, that is, P(15 < X < 20)

P(15 < X < 20) = P(X < 20) - P(X ≤ 15)

These probabilities will be evaluated using a cumulative frequency calculator.

P(X < 20) = 0.65092

P(X ≤ 15) = poissoncdf(18, 15) = 0.28665

P(15 < X < 20) = P(X < 20) - P(X ≤ 15) = 0.65092 - 0.28665 = 0.36427.

You can use the Poisson distribution calculator here

https://stattrek.com/online-calculator/poisson.aspx