Math Problem Statement

A quality-control engineer inspects a random sample of 3 batteries from each lot of 24 car batteries ready to be shipped. If such a lot contains 6 batteries with slight defects, what probabilities that the inspector's sample will contain only one battery with defect? (Round to 4 digits after dot) Select one:

0.8168

0.1832

0.5464

0.4536

Solution

To solve this problem, we need to use the hypergeometric distribution since the sample is drawn without replacement from a finite population.

The hypergeometric distribution describes the probability of kk successes (defective batteries) in a sample of size nn, drawn from a population of size NN, containing KK successes (defective batteries).

Given information:

  • Total number of batteries in the lot (NN) = 24
  • Number of defective batteries in the lot (KK) = 6
  • Number of batteries inspected in the sample (nn) = 3
  • We need to find the probability that exactly 1 defective battery (k=1k = 1) is in the sample.

The formula for the hypergeometric probability is:

P(X=k)=(Kk)(NKnk)(Nn)P(X = k) = \frac{\binom{K}{k} \binom{N - K}{n - k}}{\binom{N}{n}}

Where:

  • (Kk)\binom{K}{k} is the number of ways to choose kk defective batteries from KK defective batteries.
  • (NKnk)\binom{N - K}{n - k} is the number of ways to choose the remaining nkn - k non-defective batteries from the NKN - K non-defective batteries.
  • (Nn)\binom{N}{n} is the total number of ways to choose nn batteries from the population of NN.

Plugging in the values:

  • K=6K = 6
  • N=24N = 24
  • n=3n = 3
  • k=1k = 1

First, calculate the binomial coefficients:

(61)=6,(182)=18×172=153,(243)=24×23×226=2024\binom{6}{1} = 6, \quad \binom{18}{2} = \frac{18 \times 17}{2} = 153, \quad \binom{24}{3} = \frac{24 \times 23 \times 22}{6} = 2024

Now, use these values in the formula:

P(X=1)=6×1532024=91820240.4536P(X = 1) = \frac{6 \times 153}{2024} = \frac{918}{2024} \approx 0.4536

Answer:

The probability that the sample will contain exactly one defective battery is 0.4536.

Would you like to explore more examples or details about the hypergeometric distribution? Here's a list of related questions:

  1. What is the probability of getting 0 defective batteries in the sample?
  2. How does the probability change if there are 8 defective batteries in the lot?
  3. What is the difference between the binomial and hypergeometric distributions?
  4. How do you calculate probabilities with replacement versus without replacement?
  5. What are some real-world examples where the hypergeometric distribution applies?

Tip: When dealing with probabilities without replacement, always consider the hypergeometric distribution instead of binomial, as the population is finite and the events are not independent.

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Math Problem Analysis

Mathematical Concepts

Probability
Hypergeometric Distribution
Combinatorics

Formulas

P(X = k) = (C(K, k) * C(N-K, n-k)) / C(N, n)

Theorems

Hypergeometric Probability Theorem

Suitable Grade Level

College Level / Advanced High School