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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