SOLUTION: 1.Consider a production of 450 parts, 50 parts of them do not conform to customer requirements, four parts are selected randomly. What is the probability that at least two of them
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Question 1163204: 1.Consider a production of 450 parts, 50 parts of them do not conform to customer requirements, four parts are selected randomly. What is the probability that at least two of them do not conform to customer requirements.
Answer by solver91311(24713) (Show Source): You can put this solution on YOUR website!
Probability of a bad part for any random selection: 
Probability of at least two successes out of four trials with a probability of success = 
:
\ =\ \sum_{r=2}^4\,\ {{4}\choose{r}}\,(\frac{1}{9}\)^r\,\cdot\,\(\frac{8}{9}\)^{4-r})
However, the following is equivalent and less arithmetic:
\ =\ 1\ -\ P\(\leq\,1,4,\frac{1}{9}\)\ =\ 1\ -\ \sum_{r=0}^1\,{{4}\choose{r}}\,(\frac{1}{9}\)^r\,\cdot\,\(\frac{8}{9}\)^{4-r})
John
My calculator said it, I believe it, that settles it
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