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MEASURES OF VARIATION How dispersed, how spread out is the data? Study Guide: Variation Browse pages 88-98 in your textbook One number may not represent an entire set of numbers well so, a cross reference is__________? Name 3 measures of variation Provide advantages and disadvantages of the range The measurement that helps us see how the data is different from the mean is____________? Why divide by n-1 sometimes and by N other times? Obtuse Ollie believes he has discovered an easier method for ex 5 (Big Blossom Greenhouse) E(8-5.5)^2/7= Comment on his new formula Compare and contrast sample and population formulas for the mean and for standard deviation Study Guide A cross reference is the measure of dispersion/variation/fluctuation/spread The big 3 are: range; variance; and standard deviation Adv of r= easily computed… hi—lo disadv= doesn’t tell us the distance individuals are from the typical/mean The standard deviation N—1 is for the sample standard deviation population data N is used with Ollie is using the median, not the mean which is required The formulas for mean are the same regardless of whether we have sample or pop data. The formulas for s and little sigma are nearly the same, except for the denominator n--1 More measures of Spread Stay tuned for the coefficient of variation CV which allows us to directly compare 2 separate groups/populations! And stay awake for Chebyshev’s Theorem which works for any data and and constant >1

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