Transcript Variance.

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What does dispersion in statistics mean?
Dispersion means how spread out the data is in a
data set. In other words, how much of the data is
close to or far away from the mean or average.
Remember….so far, we have discussed how to find
one number that represents the data (measure of
central tendency) as well as different ways to
display data…box and whisker plots, frequency
tables and histograms.
By finding the variance and standard
deviation.
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Deviation just means how far from the normal
The Standard Deviation is a measure of how spread out numbers are.
Its symbol is σ (the greek letter sigma)
The formula is easy: it is the square root of the Variance. So now you ask,
"What is the Variance?“
The Variance is defined as:
The average of the squared differences from the Mean.
To calculate the variance follow these steps:
Work out the mean then for each number: subtract the Mean and square the
result. Then work out the average of those squared differences.
Calculator steps to find the variance:
◦ First, you must type the data values into the
calculator to do this, use the following calculator
steps: STAT, ENTER and then type the data values
into L1.
◦ Second, you must go to the catalog to find the
variance. The calculator steps to do this are: 2nd, 0
and then scroll down to the word Variance.
◦ Third, you are finding the variance of the data you
put into L1 so you hit the 2nd button and then 1.
Enter.
 This is the variance.
◦ First, find the variance
◦ Second, find the square root of the variance.
◦ This is the standard deviation!!!!