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mariomintchev

  • 3 years ago

Can someone explain the STANDARD DEVIATION OF THE DIFFERENCES formula to me?

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  1. mariomintchev
    • 3 years ago
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    @jagatuba @Jemurray3 @jhonyy9 @karatechopper @phi @robtobey @satellite73

  2. mariomintchev
    • 3 years ago
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    I am given 2 sets of 10 numbers. How do I plug them into this formula to get the correct answer?

  3. jhonyy9
    • 3 years ago
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    so what numbers you have got for ????

  4. mariomintchev
    • 3 years ago
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  5. jhonyy9
    • 3 years ago
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    the sum across the values how you can get it ?

  6. mariomintchev
    • 3 years ago
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    im confused about the top part of the formula. ive been getting the wrong answers so i must be doing something wrong.

  7. jhonyy9
    • 3 years ago
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    sorry but this attachement i not can opening ,not id compatibly with my excell programm

  8. mariomintchev
    • 3 years ago
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  9. mariomintchev
    • 3 years ago
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    what about now?

  10. jhonyy9
    • 3 years ago
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    can you rewrite me here the values for x and X the mean or average and the value for n ?

  11. jhonyy9
    • 3 years ago
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    @robtobey can you opening this attachement please ?

  12. mariomintchev
    • 3 years ago
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    (column 1) x = 129, 237, 110, 32, 322, 134, 119, 32, 172, 149 total sum for x = 1436 mean for x = 143.6 (column 2) y = 130, 224, 113, 38, 320, 124, 122, 33, 169, 148 total sum for y = 1421 mean for y = 142.1 value for n = 10 df = n-1 (so 9)

  13. jhonyy9
    • 3 years ago
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    have you any idea for this ?

  14. mariomintchev
    • 3 years ago
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    yes but ive been getting the wrong answers. d bar = 1.5 so ive been doing ((129-1.5)^2+(237-1.5)^2+(110-1.5)^2+.......))

  15. jhonyy9
    • 3 years ago
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    so how i see it there will be in numerator sqrt(sum(x-X)^2) divide by sqrt9 so divide by 3 ok ?

  16. jhonyy9
    • 3 years ago
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    can you calcule first this sum ?

  17. jhonyy9
    • 3 years ago
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    how many will be this sum ?

  18. mariomintchev
    • 3 years ago
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    i got 270258.5 for x and 261262.5 for y then i subtracted the 2 to get 8996

  19. mariomintchev
    • 3 years ago
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    then divide by 9 and square root it to get 31.616

  20. mariomintchev
    • 3 years ago
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    but thats wrong

  21. jhonyy9
    • 3 years ago
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    why divide by 9 and not by 3 ?

  22. mariomintchev
    • 3 years ago
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    arent u supposed to do whats in the radical first and then square root it?

  23. jhonyy9
    • 3 years ago
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    why you can separte it sqrt of numerator and sqrt of denominator and vide it after

  24. jhonyy9
    • 3 years ago
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    and divide it after

  25. mariomintchev
    • 3 years ago
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    i get the same answer either way

  26. mariomintchev
    • 3 years ago
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    31.616

  27. mariomintchev
    • 3 years ago
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    the right answer is 5.93

  28. robtobey
    • 3 years ago
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    @jhonyy9 It may to late for solving this problem. Attached is a screen capture of part of the xls file. I am running on a mid 2010 IMac with 8Gb of ram to support virtual versions of Windows XP pro, Windows 98SE and in the past Ubuntu Linux. The xls file is not a normal spread sheet data file. All I can provide is a screen capture of what I see.

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  29. jhonyy9
    • 3 years ago
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    how can i opening it what program i need using for ?

  30. mariomintchev
    • 3 years ago
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    i provided all the necessary info above ^^^^^

  31. jhonyy9
    • 3 years ago
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    so than you need calcule right this sum and after make the squareroot of them ,yes ?

  32. jhonyy9
    • 3 years ago
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    so and after just divide it by 3

  33. robtobey
    • 3 years ago
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    Ask @mariomintchev what version of Excel did she/he use to generate the spread sheet.

  34. mariomintchev
    • 3 years ago
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    Excel 2010

  35. mariomintchev
    • 3 years ago
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    SCREENSHOT

  36. phi
    • 3 years ago
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    They want the standard deviation of the differences. Your formula tells you how to find the standard deviation of a list of numbers. The first step is find the list of numbers: the list of differences so find x-y where x= 129, 237, 110, 32, 322, 134, 119, 32, 172, 149 y = 130, 224, 113, 38, 320, 124, 122, 33, 169, 148 the differences (call it z) are z= -1 13 -3 -6 2 10 -3 -1 3 1 now use your formula to find the standard deviation

  37. mariomintchev
    • 3 years ago
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    so ((-1-1.5)^2+(13-1.5)^2+(-3-1.5)^2+....)) ???

  38. phi
    • 3 years ago
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    yes, then divide by 9 then take the square root.

  39. mariomintchev
    • 3 years ago
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    ok, i got 5.95 so its close enough. thanks phi, i can always rely on you!

  40. phi
    • 3 years ago
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    I got 5.930 (dd-1.5).^2 6.2500 132.2500 20.2500 56.2500 0.2500 72.2500 20.2500 6.2500 2.2500 0.2500 sum(ans)/9 = 35.1667 sqrt(35.1667)= 5.9302

  41. mariomintchev
    • 3 years ago
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    i must have made a little mistake somewhere when punching in all of those numbers and parenthesis. i understand what i need to do now though. thanks! =o)

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