tells nothing of the way that the data is distributed between the two
extremes.
Compare two distributions, A and B, both with the same range
(30).
DISTRIBUTION A
DISTRIBUTION B
60
60
61
85
67
87
73
89
90
90
7.
ARITHMETIC MEAN.
a. This is the simplest and most used of all methods. It is usually
referred to as just the MEAN or the AVERAGE. It is found by dividing the
sum of several values by the number of values.
Where X = Arithmetic mean
= Greek capital sigma meaning sum of
X = Each individual value
N = Number of values
b. The mean is used to indicate the average grade of a group of
students, the average height of a group of people, etc, where the values are
all weighted the same.
c. There are several shortcut methods employed in the computation of
the mean, especially when the data have certain characteristics. Consider
the data that led to the graph shown in figure 5. The graph itself is made
up of grouped data. For example, there were 12 readings between 97.50 and
98.49, but rather than take each one individually, we assumed them to all
be at 98.00.
At the expense of a slight error, this process greatly
simplified the construction of the graph.
The use of grouped data also
greatly simplified the computation of the mean. The work is shown in the
following table.
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