Standard diviation is a statistical measure of variation of a set of scores and tells us how much, on average, scores differ from the mean. A large SD tells us that the scores are spread widely, a small SD that results are less soread out.

work out the average: (2+3+4)/3=3

minus the average from each starting result: 2-3=-1, 3-3=0, 4-3=1

square the last 3 results: 1, 0, 1

add these new results together: 1+1+0=2

subtract 1 from the number of observations in the group: 3-1=2

Divide the sum of the squares by the last value found: 0

square root of last answer: 0/0=0

Advantages: The value of each score is taken into account, it is a most sensitive measure of dispersion,used in advanced statistical procedures.

Disadvantages: complicated to work out

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