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Standard deviation of a set

This topic has 5 member replies
pkw209 Master | Next Rank: 500 Posts Default Avatar
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Standard deviation of a set

Post Mon May 03, 2010 2:13 pm
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    Is the standard deviation of the set of measurements x1, x2, x3....x20 less than 3?

    A) The variance for the set of measurements is 4.

    B) For each measurement, the difference between the mean and that measurement is 2.

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    liferocks Legendary Member Default Avatar
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    Post Mon May 03, 2010 5:38 pm
    variance of a set=average of square root of difference between the mean and that measurements

    and standard deviation=square root of variance

    since both conditions provides the variance either is sufficient

    Hence ans D

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    tanviet Legendary Member Default Avatar
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    Post Tue May 04, 2010 12:36 am
    pls, help

    what is variance?

    liferocks Legendary Member Default Avatar
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    Post Tue May 04, 2010 12:42 am
    duongthang wrote:
    pls, help

    what is variance?
    You can get a detail definition here http://en.wikipedia.org/wiki/Variance

    in simple word for a series
    x1,x2,x3.. if mean is x

    variance =[(x-x1)^2+(x-x2)^2+(x-x3)^2]/3

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    ajith Legendary Member
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    Post Tue May 04, 2010 2:51 am
    pkw209 wrote:
    Is the standard deviation of the set of measurements x1, x2, x3....x20 less than 3?

    A) The variance for the set of measurements is 4.

    B) For each measurement, the difference between the mean and that measurement is 2.
    Variance in this Example is if mean is m

    (m-x1)^2+(m-x2)^2 ......+ (m-x20)^2)/20

    Standard deviation is the square root of the variance.

    a) Variance =4 ; SD = 2
    b) Variance = (2^2+2^2.....+2^2)/20 = 2^2 = 4; SD = 2

    A and B are independently sufficient! D

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    gmatmachoman Legendary Member Default Avatar
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    Post Tue May 04, 2010 5:38 am
    ajith wrote:
    pkw209 wrote:
    Is the standard deviation of the set of measurements x1, x2, x3....x20 less than 3?

    A) The variance for the set of measurements is 4.

    B) For each measurement, the difference between the mean and that measurement is 2.
    Variance in this Example is if mean is m

    (m-x1)^2+(m-x2)^2 ......+ (m-x20)^2)/20

    Standard deviation is the square root of the variance.

    a) Variance =4 ; SD = 2
    b) Variance = (2^2+2^2.....+2^2)/20 = 2^2 = 4; SD = 2

    A and B are independently sufficient! D
    @ajith bhai,

    I thought u r gone with the wind!! Bhai i was missing u ...as i had some doubts in set theory..luckily LR bhai chipped in and solved couple of them..

    @LR thanks..

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