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The sum of the values divided by the number of values. The symbol for the mean of a sample is Xbar and the symbol for a population mean is µ. 


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The nth root of the product of all the values. It is especially useful for averaging rates of change and index numbers. It minimizes the importance of extreme values. A second use of the geometric mean is to find the mean annual percent change over a period of time. For example, if gross sales were $245 million in 1985 and $692 million in 2007, what is the average annual percent increase? 


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The mean of the deviations from the mean, disregarding signs. It is abbreviated as MD. 


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A value that shows the spread of a data set. The range, variance, and standard deviation are measures of dispersion. 


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A single value that is typical of the data. It pinpoints the center of a distribution. The arithmetic mean, weighted mean, median, mode, and geometric mean are measures of central location. 


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The value of the middle observation after all the observation have been arranged from low to high. For example, if observations 6,9, 4 are rearranged to read 4, 6, 9, the median is 6, the middle value. 


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The value that appears most frequently in a set of data. For grouped data, it is the midpoint of the class containing the largest number of values. 


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It is a measure of dispersion. The range is found by subtracting the minimum value from the maximum value. 


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The square root of the variance. 


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A measure of dispersion based on the average squared difference from the arithmetic mean. 


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Each value is weighted according to it's relative importance. For example, if 5 shirts cost $10 each and 20 shirts cost $8 each, the weighted mean price is $8.40: [(5X$10)/(20X$8)]/25 = $8.40 

