Math Problem Statement

A nurse has found that when a patient calls the medical advice line claiming to have the flu, there is a 17% chance that the patient truly has the flu. Of the next 24 patients, we are interested in how many actually have the flu.

Solution

Let's go through each part of the problem shown in the image to address the errors and verify correct values.

Problem Setup:

We are dealing with a Binomial Distribution, XB(n=24,p=0.17)X \sim B(n=24, p=0.17), where:

  • n=24n = 24 (the number of patients),
  • p=0.17p = 0.17 (the probability a patient actually has the flu).

1. Probability that exactly 9 patients have the flu:

The formula for a binomial probability is:

P(X=k)=(nk)pk(1p)nkP(X = k) = \binom{n}{k} \cdot p^k \cdot (1-p)^{n-k}

Where:

  • n=24n = 24,
  • k=9k = 9,
  • p=0.17p = 0.17.

Let me calculate that.The correct probability that exactly 9 out of 24 patients actually have the flu is approximately 0.00948, not 0.08776 as shown in the image.

2. Probability that fewer than 3 of the 24 patients actually have the flu:

This involves calculating the sum of the probabilities for X=0X = 0, X=1X = 1, and X=2X = 2:

P(X<3)=P(X=0)+P(X=1)+P(X=2)P(X < 3) = P(X = 0) + P(X = 1) + P(X = 2)

Let me calculate this.The correct probability that fewer than 3 out of 24 patients actually have the flu is approximately 0.19988, not 0.2625 as shown.

3. Mean of the Distribution:

The mean of a binomial distribution is given by:

μ=np\mu = n \cdot p

Substituting the given values n=24n = 24 and p=0.17p = 0.17:

μ=240.17=4.08\mu = 24 \cdot 0.17 = 4.08

This is correct as shown in the image.

4. Standard Deviation of the Distribution:

The standard deviation of a binomial distribution is:

σ=np(1p)\sigma = \sqrt{n \cdot p \cdot (1 - p)}

Let me calculate that for you.The correct standard deviation of the distribution is approximately 1.84, not 1.83 as shown in the image.

Summary of corrections:

  1. Probability that exactly 9 patients have the flu: 0.00948 (corrected from 0.08776).
  2. Probability that fewer than 3 patients have the flu: 0.19988 (corrected from 0.2625).
  3. Mean of the distribution: 4.08 (correct).
  4. Standard deviation of the distribution: 1.84 (corrected from 1.83).

Would you like to go over any details or ask further questions?

Follow-up questions:

  1. What is the probability that exactly 0 patients have the flu?
  2. What is the cumulative probability that at most 5 patients have the flu?
  3. How would the probability change if the flu probability increased to 25%?
  4. Can you calculate the probability that exactly 12 patients have the flu?
  5. What is the variance of this binomial distribution?

Tip: For binomial distributions, always check if using a normal approximation makes sense when nn is large and pp is not too close to 0 or 1.

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Math Problem Analysis

Mathematical Concepts

Probability
Binomial Distribution

Formulas

P(X = k) = (n choose k) * p^k * (1 - p)^(n - k)
Mean: μ = n * p
Standard deviation: σ = sqrt(n * p * (1 - p))

Theorems

Binomial Theorem
Probability Theory

Suitable Grade Level

College level (Statistics)