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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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