Measure of Dispersion

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Measure of Dispersion

  1. 1. 12.3 Measures of Dispersion<br />
  2. 2. Range<br />The difference between the highest and lowest data values<br />Range = highest – lowest<br />
  3. 3. Example 1<br />Find the range for a set of data:<br />A. 10, 20, 30, 40, 50<br />B. 84, 30, 90, 59, 67, 29<br />
  4. 4. Standard Deviation<br />Dependent on all of the data items<br />Found by determining how each value deviates (or differs) from the mean<br />
  5. 5. Computing the standard deviation for a data set<br />1. Find the mean of the data items.<br />2. Find the deviation of each data from the mean<br /> data item – mean<br />3. Square each deviation<br /> (data item – mean) 2<br />4. Sum the squared deviations<br /> ∑ (data item – mean) 2<br />
  6. 6. Cont…<br />5. Divide the sum by n-1 where n represents the number of items.<br />∑ (data item – mean) 2<br /> n-1<br />6. Take the square root of the answer.<br /> √ ∑ (data item – mean) 2<br />n-1<br />

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