Math Problem Statement

13 percent are left handed. 5 randomly selected. What is the probability of there being exactlcy 3 lefties in the group

Solution

This is a binomial probability problem, where we want to find the probability of exactly 3 left-handed people out of 5 randomly selected individuals.

The binomial probability formula is:

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

Where:

  • n=5n = 5 (the total number of trials, i.e., the number of people selected),
  • k=3k = 3 (the number of successful outcomes, i.e., 3 left-handed people),
  • p=0.13p = 0.13 (the probability of success on a single trial, i.e., being left-handed),
  • (nk)\binom{n}{k} is the binomial coefficient, representing the number of ways to choose 3 lefties out of 5 people.

Step-by-Step Calculation:

  1. Binomial coefficient (nk)\binom{n}{k}: (53)=5!3!(53)!=5×42×1=10\binom{5}{3} = \frac{5!}{3!(5-3)!} = \frac{5 \times 4}{2 \times 1} = 10

  2. Calculate pkp^k: pk=0.133=0.13×0.13×0.13=0.002197p^k = 0.13^3 = 0.13 \times 0.13 \times 0.13 = 0.002197

  3. Calculate (1p)nk(1 - p)^{n-k}: (1p)nk=0.872=0.87×0.87=0.7569(1 - p)^{n-k} = 0.87^2 = 0.87 \times 0.87 = 0.7569

  4. Multiply all parts together: P(X=3)=10×0.002197×0.7569=0.01663P(X = 3) = 10 \times 0.002197 \times 0.7569 = 0.01663

Final Answer:

The probability of having exactly 3 left-handed people in the group is approximately 0.01663, or 1.663%.

Would you like more details or have any questions?


Here are 5 related questions:

  1. What is the probability of having at least 3 left-handed people in the group?
  2. What is the probability of having no left-handed people in the group?
  3. How does the probability change if 10 people are selected instead of 5?
  4. How would you calculate the expected number of left-handed people in this group?
  5. What is the probability of having exactly 2 left-handed people?

Tip: When dealing with binomial problems, always make sure you identify the number of trials, success probability, and how many successes you're looking for.

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Math Problem Analysis

Mathematical Concepts

Probability
Binomial Distribution

Formulas

P(X = k) = C(n, k) * p^k * (1-p)^(n-k)

Theorems

Binomial Theorem

Suitable Grade Level

Grades 9-12