Wednesday, March 25, 2009

Standard deviation

A conclusion is drawn from a sample of data. e.g. a conclusion can be drawn from the time usage of 50 internet users. these 50 users are a sample of all internet users.
if a conclsion has to be drawn from the population thatwill be impractical. So a sample of the population is selected an used. This means that the deviation from the mean is important.
Steps for calculating standard deviation
  1. find the mean
  2. subtract the mean from each member
  3. square the difference
  4. find the sum of these squares
  5. divide this sum by n-1
  6. find the square root of this result

3 comments:

  1. standard deviation measures the spread of the data about the mean value.
    it is useful in comparing sets of data which may have the same mean but a different range.

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  2. standard deviation is
    subtracting the original numbers from the mean of all the numbers,
    squaring the difference,
    adding the squared differences up and dividing it by the number of terms,
    and find the square root of it

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  3. In probability and statistics
    the standard deviation is ameasure of dispersion of a collection of
    values.

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