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Probabilty and Statistics..........?
A lot of 100 semiconductor chips contains 20 that are defective. Two chips are selected at random, without replacement from the lot.
1. What is the probability that the first one selected is defective?
2.What is the probability that the second one selected is defective given that the first one defective?
3. What is the probability that both are defective?
2 Answers
- Anonymous1 decade agoFavorite Answer
1. probality that first one selected is defective is = 20/100 = 1/5 = 0.20
2. probality that second one is defective = 19/ 99 = 0.19
3. probality that both are defective = 1/5 + 19/99 = 194/ 495 = 0.39
Source(s): my knowledge of maths - 1 decade ago
The probability of an event happening is number of times it happens divided by (/) the number of total times it can happen, so...
1) If the defects happen in 20 of the 100 total chips, you have your fraction. Converting a fraction to a percentage is just a simple matter of multiplying (*) by 100.
2) Now you have one less defective chip over (/) one less total chips (and there's your fraction).
3) The probability of two events happening given the probability of each is the probability of the first times the probability of the second. For example, the probability of a coin landing heads-up is 50% (or .5). The probability of a coin landing heads-up twice in a row is 50% * 50% or 25% (or .25). Knowing this, you should be able to calculate the answer to number 3 (hint: use your first two answers :-)
Source(s): <self>
