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Math Help - statistic 2 help pls

  1. #1
    pinksapphire168
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    Unhappy statistic 2 help pls

    Hi Everyone,

    I am new to the forum and really need so help before I have a test tomorrow. I have been going over my book and working through the problems but I am stuck on this problem. Would someone please help me? thank you very much for your time

    From a study
    average height of men =68in sd=2.7inch
    average forearm length=18in sd 1inch r=0.80

    a) what percentage of men have forearms which are 18 inches long to the nearest inch? for this problem I figured out 38%

    b) of the men who are 68inches tall, what percentage have forearms which are 18 inches long to the nearest inch?

    I know that the nearest inch refers to 17.5 and 18.5 and the answer in the back of the book is 60% however, I do not know how they solve the problem to get 60%
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  2. #2
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    Quote Originally Posted by pinksapphire168
    Hi Everyone,

    I am new to the forum and really need so help before I have a test tomorrow. I have been going over my book and working through the problems but I am stuck on this problem. Would someone please help me? thank you very much for your time

    From a study
    average height of men =68in sd=2.7inch
    average forearm length=18in sd 1inch r=0.80

    a) what percentage of men have forearms which are 18 inches long to the nearest inch? for this problem I figured out 38%

    b) of the men who are 68inches tall, what percentage have forearms which are 18 inches long to the nearest inch?

    I know that the nearest inch refers to 17.5 and 18.5 and the answer in the back of the book is 60% however, I do not know how they solve the problem to get 60%
    Let us determine how many standard deviations we moved to the right. Let z represent that number. Then, \mu+z\sigma =19.5 since we know the values of these substitute them inside the equation,
    18+2.7z=18.5 solving we get z\approx .18. Looking up this value on the distribution table we find that \approx .071 That tells us that approximately 7.1% are above 18 and below 18.5. Thus, since everything is in symettry over here the same applies to above 17.5 and below 18 is also 7.1%. Thus, in total we have approximately 14.2%.
    The table which was used can be found at
    http://www.statsoft.com/textbook/sttable.html
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