A community for students.

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing


  • 4 years ago

Fool's problems of the day, Two very easy problems on probability, \(1.\) Hermoine and Ron decide to check if Harry is under a dark spell. They used the the secrecy sensor to check and realized that he indeed is under it. The probability of the secrecy sensors to read dark spell if the person is under it, is \(\frac 9 {10} \). But, Hermoine tells Ron that according the book "Wizarding History", only one in a thousand gets affected by this spell.What is the probability that Harry is actually under the spell? \(2.\) Probability of giving right answer by a student is \(\frac 13 \). If eight questions are asked to a student one after the other, what is the probability that a student gives at least two right answer? Good luck and Enjoy!

  • This Question is Closed
  1. anonymous
    • 4 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Simple application of Bayes' Theorem for problem one. Problem two take the complement of the probability of the student getting 0 right answers or 1 right answer. I won't put answers for either so people can try them out :)

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

    • Attachments:

Ask your own question

Sign Up
Find more explanations on OpenStudy
Privacy Policy

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...


  • 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.