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The values in a population as a whole. 


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The values of a sample (n). 


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Several values can describe this, including; mode, median, mean, outliers, weighted mean, percentiles, and quartiles. 


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Only measure of central tendency on a nominal scale, the most frequent item in the data set. 


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The value that has an equal number of items above and below it. 


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The arithmetic average and is the most common measurement of central tendency when data are measured on an interval or ratio scale. 


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Rare observations in the tail of a distribution. 


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Calculated from data arranged in a frequency distribution. x = Σfx/Σf Σfx = sum of products (values of x and their frequencies) Σf = sample size (n) 


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Divide up an array of data into 100 slices. So if you score in the 90th percentile 90/ of other people scored below you. 


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Divides the bottom quarter from the top three quarters and is the same as the 25th percentile. 


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Also called the median (50th percentile), it divides the bottom two quarters from the top two quarters. 


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Divides the top quarter from the bottom three quarters. 


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The variation in observations around the mean (or median). 


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The difference between the largest and smallest items in the sample. 


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The differences between the third and first quartiles and represents the spread of the middle 50% of the (ordered) values. 


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Used to illustrate the locations of the median, interquartile range, and range, and is often used to compare these characteristics in different groups. 


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A measure of the average amount by which each observation is a series of observations differs from the mean. 


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Definition
Represents the average of the squared deviations in the sample. 

