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Statistics - finding the mean

  1. Jan 17, 2009 #1
    1. The problem statement, all variables and given/known data

    From the data:
    x=-5 -4 -3 -2 -1 0 1 2 3 4 5
    y= 1 5 4 7 10 8 9 13 14 13 18

    These values are in a table, ie -5 corresponds to 1, -4 to 5 and so on.
    I have to find:
    Sxx=Sum of [x(i) - mean of x]^2

    Sxy=Sum of [x(i) - mean of x][y(i) - mean of y]

    Im not sure how to do this. Whats the mean of x?

    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Jan 17, 2009 #2

    HallsofIvy

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    The mean is just the arithmetic average of the numbers. In this case, since there are 11 values for each of x and y, add the numbers and divide by 11.
     
  4. Jan 17, 2009 #3
    x is not a variable, the numbers are just -5, -4, -3 ...3,4,5
    so when you add them up you'l just get zero.
    This is what is confusing me.
     
  5. Jan 17, 2009 #4

    HallsofIvy

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    If x is -5, 4, ..., 4, 5, then it's pretty darn variable! What do you think "variable" means?

    Is said before that the mean is the average: sum divided by 11. What is 0/11? Why is that confusing?

    It is true here that you x values form an arithmetic sequence with an odd number of values: and the mean of such a sequence is the middle value.
     
  6. Jan 17, 2009 #5
    Did you mean Mean or Median?
     
  7. Jan 17, 2009 #6
    In this situation the mean and the median are the same.
     
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