Binomial Distribution: Calc Prob of 0, 1, 2 Defectives & Cost Estimate

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Probability, Combinatorics, Applied Math".In summary, the conversation discusses the use of a particular type of electronic component in PCs, which is subject to quality control checks due to a 5% defect rate. A sample of 20 components is taken from the day's output and inspected for defects, with specific criteria for accepting or rejecting the output. The binomial distribution is used to calculate the probabilities of 0, 1, and 2 defectives in the sample, and then the probability of the day's output being accepted. A link is provided for further explanation and examples of the formula. The expected cost of a day's sampling is also mentioned, with a link provided for more information and examples.
  • #1
markhboi
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can anyone help with this:

A particular type of electronic component for use in PCs is mass produced and subject to quality control checks since it is known that 5% of all components produced in this way are defective. The quality of a day's output is monitored as follows. A sample of 20 components is drawn from the day's output (which may be assumed to be large) and inspected for defective components. If this sample contains 0 or 1 defectives the day's output is accepted, otherwise it is rejected. If it contains more than 2 defectives the output is rejected. If the sample contains 2 defective a second sample of 20 is taken. If this sample contains 0 defectives the output is accepted, otherwise it is rejected.

Use the binomial distribution to calculate the probability of

(i) 0
(ii) 1
(iii) 2

defectives in a sample of 20.

Hence calculate the probability that the day's output is accepted.

Suppose that it is estimated that it costs £200 to inspect a sample of size 20. What is the expected cost of a day's sampling?
 
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  • #2
Go through the first part of the problem first. You know N=20. Then try n=0, 1, and 2 using what you know about calculating probabilities using binomial distribution.
It states 5% of all components are defective. So how many in a sample of 20 are defective? What is the probabilities of having 0 defectives? How about 1 and 2?
Here is a link in case: http://mathworld.wolfram.com/BinomialDistribution.html
 
  • #3
thats the problem, i have no clue how to do binomial and when ever i look at it online it just blags my head, anyone help me with some step by step instructions on working it out?
 
  • #4
Here is a link: http://www.intmath.com/Counting-probability/12_Binomial-probability-distributions.php
It gives a description of the formula and examples, complete with solutions.

Once you have read through the page, move on to your question. It is a lot like the problems on the page. The important step is to identify the variables. Try (i) - the probably of 0 being the number of defective samples. Thus x=0. You are taking 20 total samples, so n=20. You are also given the probability that 5% are defective. Now it is a matter of plugging everything in the formula.
 
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  • #5
Moderator's note: thread moved from "Set Theory, Logic, Probability, Statistics"
 

Related to Binomial Distribution: Calc Prob of 0, 1, 2 Defectives & Cost Estimate

1. What is the binomial distribution?

The binomial distribution is a probability distribution that describes the likelihood of a certain number of successes in a fixed number of independent trials, each with a binary outcome (e.g. success or failure).

2. How do you calculate the probability of 0, 1, or 2 defectives using the binomial distribution?

To calculate the probability of 0, 1, or 2 defectives, you will need to know the number of trials, the probability of success on each trial, and the number of successes you are interested in. Then, you can use the binomial probability formula: P(x) = (nCx)(p^x)(q^(n-x)), where n is the number of trials, p is the probability of success, q is the probability of failure (1-p), and x is the number of successes you want to calculate the probability for.

3. What is the purpose of calculating the probability of defectives?

Calculating the probability of defectives allows us to assess the quality of a product or process. By understanding the likelihood of having a certain number of defective items, we can determine if the process needs to be improved or if the product meets our quality standards.

4. How can the binomial distribution be used to estimate costs?

The binomial distribution can be used to estimate costs by calculating the expected number of defectives and multiplying it by the cost of each defective item. This gives us an estimate of the total cost of defects that can be used for budgeting and decision-making.

5. Can the binomial distribution be used for non-binary outcomes?

No, the binomial distribution is specifically designed for binary outcomes (e.g. success or failure). If the outcomes are not binary, a different probability distribution, such as the Poisson distribution, may be more appropriate.

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