Probability: Draw Same Color/Number Chips & Find Defective Bulbs

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Discussion Overview

The discussion revolves around two probability problems: one involving the drawing of colored and numbered chips from a bowl, and the other concerning the examination of light bulbs to determine the likelihood of finding defective ones. The scope includes mathematical reasoning and problem-solving strategies related to probability theory.

Discussion Character

  • Mathematical reasoning
  • Homework-related
  • Technical explanation

Main Points Raised

  • One participant presents a scenario with 5 red and 3 blue chips and proposes calculating the probability of drawing two chips that are either the same color or have the same number.
  • Another participant suggests that initial effort is required before receiving help, recommending the listing of all possible outcomes.
  • A participant describes their approach to the first question, considering three cases for calculating probabilities and arriving at an answer of 4/7, seeking confirmation of its correctness.
  • For the second question, the same participant calculates the probability of finding at least one defective bulb using the complement method, yielding 1 - 48C5/50C5, but expresses difficulty with the second part of the question.
  • Further inquiries are made regarding the additive nature of probabilities for different combinations in the first problem, emphasizing the need to consider all relevant cases.
  • In the second problem, participants are encouraged to explore various combinations and permutations of defective and non-defective bulbs to understand the probabilities involved.
  • One participant humorously suggests that the number of bulbs examined could be 50 to exceed a probability of 1/2, while also recommending resources for understanding binomial probability formulas.
  • There is a general emphasis on breaking down complex problems into smaller, manageable parts to facilitate understanding and calculation.

Areas of Agreement / Disagreement

The discussion reflects a mix of approaches and interpretations regarding the probability calculations, with no consensus reached on the correctness of the initial answers or methods proposed. Participants challenge and refine each other's reasoning without resolving the disagreements.

Contextual Notes

Participants express uncertainty about the correctness of their calculations and the assumptions underlying their approaches. There is a reliance on combinatorial reasoning and the need for clarity on additive probabilities, which remains unresolved.

mehtamonica
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1. There are 5 red chips and 3 blue chips in a bowl. The red chips are numbered 1,2,3,4,5 resp and the blue chips are numbered 1,2,3 resp. If 2 chips are to be drawn at random and without replacement, find the prob that these chips have either the same number or the same color.2. In a lot of 50 light bulbs, there are 2 bad bulbs. An inspector examines 5 bulbs, which are selected at random and without replacement.

a) Find the prob of atleat one defective bulb among the 5.
b) How many bulbs should be examined so that the probability of finding atleat 1 bad bulb exceeds 1/2?
 
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On this forum,you have to show some initial effort before getting help. Try listing all the possible outcomes.
 
For the first question I took 3 possible cases i) both the chips are red (ii) both the chips are blue (iii) when the no. on both the chips are the same. I added the three probabilities and got the final answer to be 4/7. I just wanted to make sure that my answer was correct.

As for the second question, the first part was simple and got the answer as 1-48C5/50C5. But the second part I was unable to solve.
 
Things to ask yourself for the first question:

a) What is the probability of getting the combination red-red?
b) What is the probability of getting the combination blue-blue?
c) Are these probabilities additive in nature?
This tells you the probability of getting the same color. (Note: your answer to this is incorrect if you added the probability of not getting the combinations)

d) What is the probability of getting 1-1?
e) What is the probability of getting 2-2?
f) What is the probability of getting 3-3?
This tells you the probability of getting the same number. Tie it all together (Yes it's additive).

Second problem:

Part A]
Like the first ask yourself...
a) What is the probability of getting the combination b-b-g-g-g, and all it's permutations?
b) What is the probability of getting the combination b-g-g-g-g, and all it's permutations?

Part B]
Exceeds 1/2? Not "just barely exceeds" 1/2. Then your answer can be 50. ;)

On a serious aside, read this: http://www.mathwords.com/b/binomial_probability_formula.htm

Find how the formula was derived. You probably have it in your probability textbook too. :) :)


Probability theory is all about taking your problem and breaking it into a laundry list of smaller easier problems.
 

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