Quantcast

A community for students. Sign up today!

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

osanseviero

  • one year ago

If I have a bag with 8 balls, 4 of them red and 4 of them white, which is the probability than when I take a sample size 2 without replacement, both balls are red. I did 1/2 X 3/7, but this only occurs if the first ball was red. If not, it is 1/2 X 4/7 and it is a different thing...so, what should I do?

  • This Question is Closed
  1. theEric
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    I'm not too great with probability, but I think you're right with \(\frac{1}{2}\times \frac{3}{7}\). You can look at it like what are the chances of picking the first ball as red and the second ball as red. First we need to pick one red ball. So you look at how many ways can you pick a red versus how many picks there are. That is \(\frac{4}{8}=\frac{1}{2}\). So now we have looked at picking the first red ball, and we move on to picking the second. There are 3 red balls out of 7 total, so \(\frac{3}{7}\). All in all, there are 4 out of 8 ways a red ball would be picked first; then, out of those 4 ways, only 3 ways out of 7 will give you a red ball. Out of all the ways to pick that exist, I think \(\frac{4}{8}\times\frac{3}{7}\) is the answer.

  2. theEric
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    I wouldn't take my solution as completely right. But I'm fairly confident... If someone else has a contradictory solution, I'd be interested in seeing where I went wrong.

  3. osanseviero
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    I think you are right :) thanks

  4. theEric
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    I would ask if you had any questions, but we found the same answer :P And, if the first ball is not red, it IS a different thing. But it's not what we are considering :) Thanks! I hope we are!

  5. Not the answer you are looking for?
    Search for more explanations.

    • Attachments:

Ask your own question

Ask a Question
Find more explanations on OpenStudy

Your question is ready. Sign up for free to start getting answers.

spraguer (Moderator)
5 → View Detailed Profile

is replying to Can someone tell me what button the professor is hitting...

23

  • Teamwork 19 Teammate
  • Problem Solving 19 Hero
  • You have blocked this person.
  • ✔ You're a fan Checking fan status...

Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.

This is the testimonial you wrote.
You haven't written a testimonial for Owlfred.