HP 48gII User's Manual
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Page 18-5
Coefficient of variation
The coefficient of variation of a sample combines the mean, a measure of
central tendency, with the standard deviation, a measure of spreading, and is
defined, as a percentage, by: V
x
= (s
x
/x)100.
Sample vs. population
The pre-programmed functions for single-variable statistics used above can be
applied to a finite population by selecting the
Type: Population in the
SINGLE-VARIABLE STATISTICS screen. The main difference is in the values
of the variance and standard deviation which are calculated using n in the
denominator of the variance, rather than (n-1).
Example 3
-- If you were to repeat the exercise in Example 1 of this section,
using
Population rather than Sample as the Type, you will get the same
values for the mean, total, maximum, and minimum. The variance and
standard deviation, however, will be given by: Variance: 0.852, Std Dev:
0.923.
Obtaining frequency distributions
The application 2. Frequencies.. in the STAT menu can be used to obtain
frequency distributions for a set of data. Again, the data must be present in
the form of a column vector stored in variable ΣDAT. To get started, press
‚Ù˜ @@@OK@@@. The resulting input form contains the following fields:
ΣDAT: the matrix containing the data of interest.
Col: the column of ΣDAT that is under scrutiny.
X-Min: the minimum class boundary (default = -6.5).
Bin Count: the number of classes(default = 13).
Bin Width: the uniform width of each class (default = 1).
Definitions
To understand the meaning of these parameters we present the following
definitions
: Given a set of n data values: {x
1
, x
2
, …, x
n
} listed in no particular
order, it is often required to group these data into a series of classes
by
counting the frequency
or number of values corresponding to each class.
(Note: the calculators refers to classes as bins).