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© 2014 Pacific Crest
309
Why?
The standard deviation must carry the same units as the data points. The calculation
could have been carried out in terms of kilometers per liter: k.p.l. (k.p.l is as common
in Europe as m.p.g. is inAmerica). When we calculate variance and standard deviation
we must attach the appropriate units. In this case, the standard deviation should have
been given as 6.5 m.p.g.
●
Not interpreting the notation of a box plot correctly
Example
:
60 65.25 70.5 75.75 81 86.25 91.5
The minimum value is 60
and the maximum value is
95. The mean is 80. and the
first and third quartiles are
65 and 92.
Why?
Box plots identify the following key information: minimum, first quartile, median,
third quartile and maximum value (and the range). The first vertical line is the
minimum at 65, the box identifies 1
st
and 3
rd
quartiles at 74 and 88, with the median
at 80 (the white line in the box), and finally the maximum at 92.
A
re You Ready?
Before continuing, you should be able to ...
I can...
OR
Here’s my question...
calculate the mean for a given set of
numbers
calculate the squared difference for a
given set of numbers
calculate the variance for a given set of
numbers
calculate the standard deviation for a
given set of numbers
P
lan
How to complete the activity
1. Think about the calculation process of the previous examples to determine what is important in the
calculation.
2. Review the model to determine if the calculation produces the expected results.
7.2 Variation