measures of central tendency cj 526 statistical analysis in criminal justice
Post on 21-Dec-2015
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Characteristics of a Measure of Central Tendency1. Single number that represents the
entire set of data (average)
The Mode
Score or qualitative category that occurs with the greatest frequency
Always used with nominal data, we find the most frequently occurring category
Mode
Example of modal category: Sample of 25 married, 30 single, 22
divorced Married is the modal category
Determined by inspection, not by computation, counting up the number of times a value occurs
Example of Finding the Mode X: 8, 6, 7, 9, 10, 6 Mode = 6 Y: 1, 8, 12, 3, 8, 5, 6 Mode = 8 Can have more than one mode 1, 2, 2, 8, 10, 5, 5, 6 Mode = 2 and 5
Finding the Median -- continued
3. If there is an even number of scores, the median corresponds to a value halfway between the two middle scores
Shape of the Distribution
Symmetrical – Mean Not symmetrical—the median will be
better Any time there are extreme scores
the median will be better
Example Median income: if someone loses
their job, an income of 0—this would pull the average down
Median housing values: an unusually nice house or poor house would affect the average
Better to use the median