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Math Help - Normal distribution.

  1. #1
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    Post Normal distribution.

    1. The following graph of a normal distribution has a mean of 75 and a standard deviation of 5.
    Normal distribution.-8-4_quiz_curve6_cbel.gif

    which of the following apply to how the shape and location of the curve would change if the mean becomes 80 and the standard deviation changes to 3.

    shifted left
    shifted right
    narrower
    broader
    same location
    same shape

    2. The following graph of a normal distribution has a mean of 20 and a standard deviation of 5.
    Normal distribution.-8-4_quiz_curve1_cbel.gif

    What percent of the data lies between 15 and 25?


    3. The following graph of a normal distribution has a mean of 8 and a standard deviation of 1.5.

    Normal distribution.-8-4_quiz_curve2_cbel.gif

    What percent of the data is greater than 6.5?
    Last edited by mr fantastic; May 12th 2010 at 09:23 PM. Reason: Re-titled.
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  2. #2
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    Quote Originally Posted by danield3 View Post
    1. The following graph of a normal distribution has a mean of 75 and a standard deviation of 5.
    Click image for larger version. 

Name:	8-4_quiz_curve6_cbel.gif 
Views:	42 
Size:	2.2 KB 
ID:	16823

    which of the following apply to how the shape and location of the curve would change if the mean becomes 80 and the standard deviation changes to 3.

    shifted left
    shifted right
    narrower
    broader
    same location
    same shape

    2. The following graph of a normal distribution has a mean of 20 and a standard deviation of 5.
    Click image for larger version. 

Name:	8-4_quiz_curve1_cbel.GIF 
Views:	38 
Size:	2.2 KB 
ID:	16824

    What percent of the data lies between 15 and 25?


    3. The following graph of a normal distribution has a mean of 8 and a standard deviation of 1.5.

    Click image for larger version. 

Name:	8-4_quiz_curve2_cbel.GIF 
Views:	11 
Size:	2.2 KB 
ID:	16825

    What percent of the data is greater than 6.5?
    1. The normal distribution is centred on the mean, the sd affects its width ....

    2. Look up your book for the rule of thumb for the probability of being within 1 sd of the mean.

    3. Use the symmetry of the distribution and the answer to Q2.

    (Note: Q2 and Q3 can be done more accurately using Z = (X - mu)/sigma and refering to a standard normal distribution table).
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