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Thread: standard deviation

  1. #1

    Thread Starter
    New Member
    Join Date
    Mar 2006

    standard deviation

    can anybody help me

    a) what does standard deviation describe about a set of data?
    b)Table below shows the crushing strengths of concrete samples, determine
    1) Mode, mean and median and standard deviation
    2) standard deviation likely for the population

    261, 245, 385, 253, 298, 284, 320, 335, 297, 335
    300, 314, 345, 310, 279, 298, 305, 298, 320, 300


  2. #2
    New Member
    Join Date
    Sep 2005

    Re: standard deviation

    well i worked out the mean to be 289.6 by adding all the numbers then dividing by how many they are Ex/n (sum of x divided by the number of terms) im doing this to for my S1 exam i hate stats

    i think to do standard deviation you square all the numbers then add them up then divide by the number of terms then subract the mean squared
    (289.6)^2 then square root the answer i'll work it out in a bit
    Last edited by peaches_2479; Apr 10th, 2006 at 06:04 AM. Reason: didnt finish what i was saying

  3. #3
    Frenzied Member conipto's Avatar
    Join Date
    Jun 2005

    Re: standard deviation

    If you just want the answer, Excel has a STDEV function that takes a range of cells and calculates it like


    However, you should really read up on statistics, as this sounds like basic statistics homework.

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  4. #4
    Addicted Member Rassis's Avatar
    Join Date
    Jun 2004

    Re: standard deviation

    For the population (point 2)), you use the function =STDEVP(A1..A#).

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  5. #5
    Addicted Member TBeck's Avatar
    Join Date
    Apr 2006
    Ontario, Canada

    Re: standard deviation

    standard deviation:

    where x bar is average

    basicly u take the first piece of data, subtract the average, square the result
    then u repeat this for your second piece of data, third, and so on, once you do this for all of your data you take the sum of these results and divide by the number of data pieces. square root and you are done

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