Math Problem Statement

Assuming that 5% of visitors are looking for other websites, find the probability that in a random sample of 5 visitors, exactly 4 are looking for the website. Round to at least three decimal places.

Solution

This problem involves calculating a binomial probability.

Problem Breakdown:

  • Given Information:
    • Probability that a visitor is looking for another website (pp) = 5% = 0.050.05.
    • Probability that a visitor is not looking for another website (q=1pq = 1 - p) = 10.05=0.951 - 0.05 = 0.95.
    • Random sample size (nn) = 5 visitors.
    • Number of successes (kk) = 4 (we want exactly 4 visitors looking for another website).

Binomial Probability Formula:

P(X=k)=(nk)pkqnkP(X = k) = \binom{n}{k} \cdot p^k \cdot q^{n-k} Where:

  • (nk)\binom{n}{k} = n!k!(nk)!\frac{n!}{k!(n-k)!} is the number of combinations.
  • pkp^k is the probability of success raised to the power kk.
  • qnkq^{n-k} is the probability of failure raised to the power nkn-k.

Step-by-Step Solution:

  1. Calculate (nk)\binom{n}{k}: (54)=5!4!(54)!=51=5\binom{5}{4} = \frac{5!}{4!(5-4)!} = \frac{5}{1} = 5

  2. Compute pkp^k and qnkq^{n-k}: pk=(0.05)4=0.00000625p^k = (0.05)^4 = 0.00000625 qnk=(0.95)1=0.95q^{n-k} = (0.95)^1 = 0.95

  3. Substitute values into the formula: P(X=4)=(54)p4qn4P(X = 4) = \binom{5}{4} \cdot p^4 \cdot q^{n-4} P(X=4)=50.000006250.95P(X = 4) = 5 \cdot 0.00000625 \cdot 0.95

  4. Perform the calculations: P(X=4)=50.0000059375=0.0000296875P(X = 4) = 5 \cdot 0.0000059375 = 0.0000296875

  5. Round to three decimal places: P(X=4)0.000P(X = 4) \approx 0.000

Final Answer:

The probability is approximately 0.000.

Would you like a breakdown of any specific step or more examples?


Related Questions:

  1. What is the probability that exactly 3 visitors are looking for other websites in the same sample?
  2. What is the probability that none of the 5 visitors are looking for other websites?
  3. How does increasing the sample size affect the binomial probability?
  4. Can the approximation using a Poisson distribution be applied here, and if so, how?
  5. How would the probability change if pp were 10% instead of 5%?

Tip:

When working with small probabilities and large sample sizes, be cautious about rounding too early, as small differences in intermediate steps can affect the final answer.

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Math Problem Analysis

Mathematical Concepts

Binomial Probability
Probability Theory

Formulas

P(X = k) = C(n, k) * p^k * q^(n-k)
C(n, k) = n! / [k!(n-k)!]

Theorems

Binomial Distribution Theorem

Suitable Grade Level

High School (Grades 9-12)