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Math Help - a couple of easy questions about probability

  1. #1
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    a couple of easy questions about probability

    hey there,
    i just cant get my head around solving these questions... my textbook has not been of much help.

    if you know the formulas i should be using, please let me know.

    What you need to know:
    12% of peoples first preference goes to cheese on crackers.

    Question:
    What is the probability that from a random sample of ten people, exactly four gave their first preference to having cheese?

    im assuming its something like .12*4 and something about .88 but im not sure what order to use and what formula.

    P(4 people want cheese)


    -----------------------------------------------------------------------

    and if you can do that, are you able to try this one also.

    Question: what is the probability that from a random sample of 10 people, a MAJORITY gave their first preference to cheese?

    Much appreciated if you can give me a heads up in the right direction
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  2. #2
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    Quote Originally Posted by HobbleBobble View Post
    hey there,
    i just cant get my head around solving these questions... my textbook has not been of much help.

    if you know the formulas i should be using, please let me know.

    What you need to know:
    12% of peoples first preference goes to cheese on crackers.

    Question:
    What is the probability that from a random sample of ten people, exactly four gave their first preference to having cheese?

    im assuming its something like .12*4 and something about .88 but im not sure what order to use and what formula.

    P(4 people want cheese)


    -----------------------------------------------------------------------

    and if you can do that, are you able to try this one also.

    Question: what is the probability that from a random sample of 10 people, a MAJORITY gave their first preference to cheese?

    Much appreciated if you can give me a heads up in the right direction
    Is the probability of having cheese on crackers the same as having or wanting cheese?

    You really need to be clearer to get the help you want.

    Also you say your text book is not too helpful. What exactly are you studying? This question sounds like it could be binomial probabilty, does this ring a bell?

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  3. #3
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    Quote Originally Posted by HobbleBobble View Post
    hey there,
    i just cant get my head around solving these questions... my textbook has not been of much help.

    if you know the formulas i should be using, please let me know.

    What you need to know:
    12% of peoples first preference goes to cheese on crackers.

    Question:
    What is the probability that from a random sample of ten people, exactly four gave their first preference to having cheese?

    im assuming its something like .12*4 and something about .88 but im not sure what order to use and what formula.

    P(4 people want cheese)


    -----------------------------------------------------------------------

    and if you can do that, are you able to try this one also.

    Question: what is the probability that from a random sample of 10 people, a MAJORITY gave their first preference to cheese?

    Much appreciated if you can give me a heads up in the right direction
    Let X be the random variable 'first preference goes to cheese on crackers'.

    X ~ Binomial(n = 10, p = 0.12).

    Calculate Pr(X = 4). Calculate Pr(X > 5).

    The formula is in your class notes and textbook - I suggest you review this material.
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