STA6166 F05-4 Measures of Center

# STA6166 F05-4 Measures of Center - Topic (4) SUMMARIZING...

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Topic (4) SUMMARIZING DATA –CENTER OR CENTRAL TENDENCY 4-1 Topic (4) SUMMARIZING DATA – CENTER OR CENTRAL TENDENCY I) QUANTITATIVE DATA a) Median (50 th percentile) Defn: The MEDIAN of a data set is the middle value. That is, when the data values are arranged from low to high, it is that value in the list such that half of the data points are smaller and the other half are larger. For even number of observations: The fish weights for the Tennessee River study ( n =12) are: 986, 1023, 1266, 1398, 917, 1763, 1459, 778, 532, 441, 544, 897 1) first order them from low to high 2) median = average of the 2 middle values. 441, 532, 544, 778, 897, 917, 986, 1023, 1266, 1398, 1459, 1763 median = 5 . 951 2 986 917 = + = m 6 of the observed values fall below m and the other 6 are larger than m

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Topic (4) SUMMARIZING DATA –CENTER OR CENTRAL TENDENCY 4-2 For odd number of observations: Thirteen fish weights are: 986, 1023, 1266, 1398, 917, 1763, 1459, 778, 532, 441, 544, 897, 1129 1) first order them from low to high 2) median = the middle value. 441, 532, 544, 778, 897, 917, 985 , 1023, 1129, 1266, 1398, 1459, 1763 m = 985 Important Point #1: The median is said to be robust because it is resistant to outliers Important Point #2: The sample median divides the total area under the bars in a histogram in half. Important Point #3:
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## This note was uploaded on 11/23/2011 for the course STA 6166 taught by Professor Staff during the Summer '08 term at University of Florida.

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STA6166 F05-4 Measures of Center - Topic (4) SUMMARIZING...

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