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Oracle Probability Interview Question

Oracle Probability Interview Question - 28 March

What is the probability of choosing the correct answer at random from the options below.

a) 1/4
b) 1/2
c) 1
d) 1/4

For Solution : Click Here


  1. Probability is 1/3.
    Since option a) and d) are same, so we have 3 different answers. Out of which 1 is correct.

    1. I'm the person who gave the 0% solution below - 1 in 3 cannot be a correct answer because it does not appear in the list (so if it was correct it would be 0% likely to be picked at random out of those 4).

      a and d being the same makes them have a probability of 2 in 4 of turning up, not 1 in 3. Not that it matters, since neither of them is on there.

      Consider each answer seperately, and check if any of them work:

      a) 1/4. Turns up twice; has 1/2 probability. These are not the same, so it doesn't work
      b) 1/2 Turns up once, hence has 1/4 probability. Again, different, so it doesn't work.
      c) 1. Turns up once, has 1/4 probability to be picked at random. Again, different.
      d) See a)

      Since you cannot pick a correct answer (all answers are incorrect), the solution is 0

    2. awesome Ans

      head off


    3. 0 cannot be the correct ans. How can u say if 1/4 turns up twice (1/2 probability) , it does not work.. Why 50% probability will not work.
      Consider this . The four answers are given . We do not know the question. Suppose the question is what is the probability of getting a head in tossing a coin. In such case the correct ans will be option b). So there can be a correct ans and it will have its probability. U cannot say all answers are wrong.

    4. It doesn't matter whether the answer is in the list. It just says what is the probability, which is either 1/3, 1/2, or 1/4. The letters a and d are the same, but still an option.

    5. For all the ones that suggest 1/3, nice thinking, but "RANDOM" is the clue word. This would not involve any choosing, so the correct answer is that the probability is 1/2 of getting one of the "1/4" options, which is the correct answer of probability when you are given 4 options. Get it?

  2. This comment has been removed by the author.

  3. Oh yay, this one is actually doable and not a paradox (replace c with 0 and you get an unsolveable paradox).

    Answer is 0. Standard 1-in-4 gives 25%, but that one is on there twice, leading to a flipping paradox between 25% and 50%. So neither of those is a stable solution. 0, however, is totally stable, given that it doesn't appear in the options - therefor, if it *is* correct, the probability of picking it is 0 out of 4, and thus it is a valid solution.


  4. I read the above comments...
    By that logic this is a trick question...
    with no option being the answer...

    How ever if be go by brute force logic :P and non-linear probability.
    option is b) 1/2

    Coz either we pick the correct answer, or we don't.. ;)

    Though I can hardly call the dibs on my answer...

  5. 1/4, because there are four answers. so the probability is 1/4.

  6. Replies
    1. look at my answer, I explained why it can't be 1/2

  7. My answer got removed. I said what ananymous said first.

  8. 1/4 because i don't need to know what is written in the options ,i just need to know how many options are(it's random pick)

  9. the Answer wud b "1" if the question dint hav the word "random" in it....since it does the logic is: >there are 4 options
    >prob of selecting any 1 option = 1/4
    >prob of the selecting the correct ans = 1
    >prob of the selected option being correct =(1/4)* 1 =1/4

  10. guys, the question doesn't imply that the answer to the question is one of the choices provided. It's not a multiple choice question. Its an open-ended question, the subject of which INVOLVES a multiple choice question. The answer is 1/3.