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Unformatted text preview: 1 Chapter 3 Describing Numerical Data 2 Measure of Central Tendency: Mean The arithmetic mean (or simply mean) of a set of data is the sum of the data values divided by the number of observations. For an entire population: For a sample: = u N x x x N x N N i i + + + = = = ..... 2 1 1 n x x x n x x n n i i + + + = = = ..... 2 1 1 3 Measure of Central Tendency: Continued The Median is the middle observation of a set of observations that are arranged in increasing (or decreasing) order. If the sample size, n, is an even number, the median is the average of the tow middle observations. The median will be located in the 0.5(n+1)th ordered position The Mode , if one exists, is the most frequently occurring value. 4 Example: Class grades for 2 sets of students Data1 Data2 61 61 68 68 77 77 81 81 82 82 82 82 87 87 96 87 96 n 8 9 mean 78 79 mode 82 82,87 median 81.5 82 5 Measure of Central Tendency The Geometric Mean is the n th root of the product of the n numbers: n n n n g x x x x x x x / 1 2 1 2 1 ) ... ( ... = = 6 Notes The mean is used to describe numerical...
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This note was uploaded on 04/29/2008 for the course EC 305 taught by Professor Rivas during the Fall '08 term at BU.
 Fall '08
 Rivas

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