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The number of emails follows a Poisson distribution with an average rate of 0.2 emails per minute. The probability mass function for a Poisson distribution is given by $P(X=k) = {lambda^k e^{-

Computer Science

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Answers

2 parts
a

0.3679\text{0.3679}

b

0.1429\text{0.1429}

Step-by-step solution

6 steps

Here's how to solve the problem using the Poisson distribution:

The number of emails follows a Poisson distribution with an average rate of 0.2 emails per minute. The probability mass function for a Poisson distribution is given by P(X=k)=λke−λk!P(X=k) = \frac{\lambda^k e^{-\lambda}}{k!}, where λ\lambda is the average number of events in the given interval.

Part a· 2 steps

What is the probability that I get no emails in an interval of length 5 minutes?

  1. Calculate the average rate λ\lambda for a 5-minute interval.

    The rate is 0.2 emails per minute. For a 5-minute interval, the average number of emails is:

    λa=0.2 emails/minute×5 minutes=1 email\lambda_a = 0.2 \text{ emails/minute} \times 5 \text{ minutes} = 1 \text{ email}
  2. Calculate the probability of getting no emails (k=0k=0) using λa=1\lambda_a = 1.

    P(X=0)=λa0e−λa0!=10e−10!=1×e−11=e−1P(X=0) = \frac{\lambda_a^0 e^{-\lambda_a}}{0!} = \frac{1^0 e^{-1}}{0!} = \frac{1 \times e^{-1}}{1} = e^{-1} P(X=0)≈0.367879P(X=0) \approx 0.367879

    The probability of getting no emails in a 5-minute interval is approximately 0.3679\boxed{\text{0.3679}}.

Part b

0.1429\text{0.1429}

What is the probability that I get more than 3 emails in an interval of length 10 minutes?

  1. Calculate the average rate λ\lambda for a 10-minute interval.

    The rate is 0.2 emails per minute. For a 10-minute interval, the average number of emails is:

    λb=0.2 emails/minute×10 minutes=2 emails\lambda_b = 0.2 \text{ emails/minute} \times 10 \text{ minutes} = 2 \text{ emails}
  2. Calculate the probability of getting more than 3 emails.

    P(X>3)=1−P(X≤3)P(X > 3) = 1 - P(X \le 3).
    This means P(X>3)=1−[P(X=0)+P(X=1)+P(X=2)+P(X=3)]P(X > 3) = 1 - [P(X=0) + P(X=1) + P(X=2) + P(X=3)].
    We use λb=2\lambda_b = 2 for these calculations.

  3. Calculate P(X=0)P(X=0), P(X=1)P(X=1), P(X=2)P(X=2), and P(X=3)P(X=3).

    P(X=0)=20e−20!=1×e−21=e−2≈0.135335P(X=0) = \frac{2^0 e^{-2}}{0!} = \frac{1 \times e^{-2}}{1} = e^{-2} \approx 0.135335 P(X=1)=21e−21!=2×e−21=2e−2≈0.270671P(X=1) = \frac{2^1 e^{-2}}{1!} = \frac{2 \times e^{-2}}{1} = 2e^{-2} \approx 0.270671 P(X=2)=22e−22!=4×e−22=2e−2≈0.270671P(X=2) = \frac{2^2 e^{-2}}{2!} = \frac{4 \times e^{-2}}{2} = 2e^{-2} \approx 0.270671 P(X=3)=23e−23!=8×e−26=43e−2≈0.180447P(X=3) = \frac{2^3 e^{-2}}{3!} = \frac{8 \times e^{-2}}{6} = \frac{4}{3}e^{-2} \approx 0.180447
  4. Sum the probabilities and subtract from 1.

    P(X≤3)=P(X=0)+P(X=1)+P(X=2)+P(X=3)P(X \le 3) = P(X=0) + P(X=1) + P(X=2) + P(X=3) P(X≤3)≈0.135335+0.270671+0.270671+0.180447=0.857124P(X \le 3) \approx 0.135335 + 0.270671 + 0.270671 + 0.180447 = 0.857124 P(X>3)=1−P(X≤3)=1−0.857124=0.142876P(X > 3) = 1 - P(X \le 3) = 1 - 0.857124 = 0.142876

    The probability of getting more than 3 emails in a 10-minute interval is approximately 0.1429\boxed{\text{0.1429}}.

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