Math Problem Statement

In a batch of 2299 calculators, there are, on average, 10 defective ones. If a random sample of 125 is selected, find the probability of having at most 2 defective units.

Only the final answer should be rounded-off to FOUR decimal places.

Solution

This problem involves a hypergeometric distribution because we are selecting a sample without replacement from a finite population.

The hypergeometric probability formula is:

P(X=k)=(Dk)(NDnk)(Nn)P(X = k) = \frac{\binom{D}{k} \binom{N-D}{n-k}}{\binom{N}{n}}

Where:

  • NN is the population size (2299 calculators),
  • DD is the number of defective calculators (10),
  • nn is the sample size (125 calculators),
  • kk is the number of defective calculators in the sample.

We are looking for the probability of having at most 2 defective calculators, so we need to calculate:

P(X2)=P(X=0)+P(X=1)+P(X=2)P(X \leq 2) = P(X = 0) + P(X = 1) + P(X = 2)

Let's calculate this step by step.

The probability of having at most 2 defective calculators in a sample of 125, selected from a batch of 2299 calculators where there are 10 defective ones, is approximately 0.9858.

Would you like further details or clarifications?

Here are 5 related questions to consider:

  1. What if the sample size was larger than 125?
  2. How does the probability change if the number of defective calculators increases?
  3. Can we use a different distribution for this problem? Why or why not?
  4. What is the probability of having exactly 1 defective unit in the sample?
  5. How would the solution change if we were sampling with replacement?

Tip: Hypergeometric distributions are ideal for sampling without replacement when the population size is not too large compared to the sample size.

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Math Problem Analysis

Mathematical Concepts

Probability
Hypergeometric Distribution

Formulas

P(X = k) = (C(D, k) * C(N-D, n-k)) / C(N, n)
P(X <= 2) = P(X = 0) + P(X = 1) + P(X = 2)

Theorems

Hypergeometric Theorem

Suitable Grade Level

Grades 11-12 or College