1. 12.3 Measures of Dispersion

2. Range The difference between the highest and lowest data values Range = highest – lowest

3. Example 1 Find the range for a set of data: A. 10, 20, 30, 40, 50 B. 84, 30, 90, 59, 67, 29

4. Standard Deviation Dependent on all of the data items Found by determining how each value deviates (or differs) from the mean

5. Computing the standard deviation for a data set 1. Find the mean of the data items. 2. Find the deviation of each data from the mean data item – mean 3. Square each deviation (data item – mean) 2 4. Sum the squared deviations ∑ (data item – mean) 2

6. Cont… 5. Divide the sum by n-1 where n represents the number of items. ∑ (data item – mean) 2 n-1 6. Take the square root of the answer. √ ∑ (data item – mean) 2 n-1